-
Notifications
You must be signed in to change notification settings - Fork 13
Expand file tree
/
Copy pathgroupby.html
More file actions
168 lines (147 loc) · 63 KB
/
groupby.html
File metadata and controls
168 lines (147 loc) · 63 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
<!DOCTYPE html>
<html lang="en-US">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>Python - groupby()</title>
<meta name="generator" content="VuePress 1.8.2">
<link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png">
<link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png">
<link rel="manifest" href="/site.webmanifest">
<link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png">
<link rel="mask-icon" href="/safari-pinned-tab.svg" color="#5bbad5">
<meta name="description" content="Example 4, Example 2, Example 3, Example 1">
<meta property="og:site_name" content="DevTut">
<meta property="og:title" content="Python - groupby()">
<meta property="og:description" content="Example 4, Example 2, Example 3, Example 1">
<meta property="og:type" content="article">
<meta property="og:url" content="/python/groupby.html">
<meta property="og:image" content="/logo.png">
<meta name="twitter:title" content="Python - groupby()">
<meta name="twitter:description" content="Example 4, Example 2, Example 3, Example 1">
<meta name="twitter:url" content="/python/groupby.html">
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:image" content="/logo.png">
<meta name="theme-color" content="#ffffff">
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="black">
<meta name="msapplication-TileImage" content="/mstile-150x150.png">
<meta name="msapplication-TileColor" content="#da532c">
<meta name="google-site-verification" content="76_rKXgwMVIjd-axJC_1zPV9OS4mEjvtgjYOWVkAdnQ">
<link rel="preload" href="/assets/css/0.styles.60619e34.css" as="style"><link rel="preload" href="/assets/js/app.1779e102.js" as="script"><link rel="preload" href="/assets/js/3.2cfa8016.js" as="script"><link rel="preload" href="/assets/js/2715.71e34515.js" as="script">
<link rel="stylesheet" href="/assets/css/0.styles.60619e34.css">
</head>
<body>
<div id="app" data-server-rendered="true"><div class="theme-container"><header class="navbar"><div class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/" class="home-link router-link-active"><!----> <span class="site-name">DevTut</span></a> <div class="links"><form id="search-form" role="search" class="algolia-search-wrapper search-box"><input id="algolia-search-input" class="search-query"></form> <nav class="nav-links can-hide"> <a href="https://github.com/devtut/generate" target="_blank" rel="noopener noreferrer" class="repo-link">
GitHub
<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav></div></header> <div class="sidebar-mask"></div> <aside class="sidebar"><nav class="nav-links"> <a href="https://github.com/devtut/generate" target="_blank" rel="noopener noreferrer" class="repo-link">
GitHub
<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav> <ul class="sidebar-links"><li><section class="sidebar-group depth-0"><p class="sidebar-heading open"><span>Python</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/python/" aria-current="page" class="sidebar-link">Disclaimer</a></li><li><a href="/python/getting-started-with-python-language.html" class="sidebar-link">Getting started with Python Language</a></li><li><a href="/python/python-data-types.html" class="sidebar-link">Python Data Types</a></li><li><a href="/python/indentation.html" class="sidebar-link">Indentation</a></li><li><a href="/python/comments-and-documentation.html" class="sidebar-link">Comments and Documentation</a></li><li><a href="/python/date-and-time.html" class="sidebar-link">Date and Time</a></li><li><a href="/python/enum.html" class="sidebar-link">Enum</a></li><li><a href="/python/set.html" class="sidebar-link">Set</a></li><li><a href="/python/simple-mathematical-operators.html" class="sidebar-link">Simple Mathematical Operators</a></li><li><a href="/python/bitwise-operators.html" class="sidebar-link">Bitwise Operators</a></li><li><a href="/python/boolean-operators.html" class="sidebar-link">Boolean Operators</a></li><li><a href="/python/operator-precedence.html" class="sidebar-link">Operator Precedence</a></li><li><a href="/python/variable-scope-and-binding.html" class="sidebar-link">Variable Scope and Binding</a></li><li><a href="/python/conditionals.html" class="sidebar-link">Conditionals</a></li><li><a href="/python/comparisons.html" class="sidebar-link">Comparisons</a></li><li><a href="/python/loops.html" class="sidebar-link">Loops</a></li><li><a href="/python/arrays.html" class="sidebar-link">Arrays</a></li><li><a href="/python/multidimensional-arrays.html" class="sidebar-link">Multidimensional arrays</a></li><li><a href="/python/dictionary.html" class="sidebar-link">Dictionary</a></li><li><a href="/python/list.html" class="sidebar-link">List</a></li><li><a href="/python/list-comprehensions.html" class="sidebar-link">List Comprehensions</a></li><li><a href="/python/list-slicing-selecting-parts-of-lists.html" class="sidebar-link">List slicing (selecting parts of lists)</a></li><li><a href="/python/groupby.html" aria-current="page" class="active sidebar-link">groupby()</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a href="/python/groupby.html#example-4" class="sidebar-link">Example 4</a></li><li class="sidebar-sub-header"><a href="/python/groupby.html#example-2" class="sidebar-link">Example 2</a></li><li class="sidebar-sub-header"><a href="/python/groupby.html#example-3" class="sidebar-link">Example 3</a></li><li class="sidebar-sub-header"><a href="/python/groupby.html#example-1" class="sidebar-link">Example 1</a></li></ul></li><li><a href="/python/linked-lists.html" class="sidebar-link">Linked lists</a></li><li><a href="/python/linked-list-node.html" class="sidebar-link">Linked List Node</a></li><li><a href="/python/filter.html" class="sidebar-link">Filter</a></li><li><a href="/python/heapq.html" class="sidebar-link">Heapq</a></li><li><a href="/python/tuple.html" class="sidebar-link">Tuple</a></li><li><a href="/python/basic-input-and-output.html" class="sidebar-link">Basic Input and Output</a></li><li><a href="/python/files-folders-i-o.html" class="sidebar-link">Files & Folders I/O</a></li><li><a href="/python/os-path.html" class="sidebar-link">os.path</a></li><li><a href="/python/iterables-and-iterators.html" class="sidebar-link">Iterables and Iterators</a></li><li><a href="/python/functions.html" class="sidebar-link">Functions</a></li><li><a href="/python/defining-functions-with-list-arguments.html" class="sidebar-link">Defining functions with list arguments</a></li><li><a href="/python/functional-programming-in-python.html" class="sidebar-link">Functional Programming in Python</a></li><li><a href="/python/partial-functions.html" class="sidebar-link">Partial functions</a></li><li><a href="/python/decorators.html" class="sidebar-link">Decorators</a></li><li><a href="/python/classes.html" class="sidebar-link">Classes</a></li><li><a href="/python/metaclasses.html" class="sidebar-link">Metaclasses</a></li><li><a href="/python/string-formatting.html" class="sidebar-link">String Formatting</a></li><li><a href="/python/string-methods.html" class="sidebar-link">String Methods</a></li><li><a href="/python/using-loops-within-functions.html" class="sidebar-link">Using loops within functions</a></li><li><a href="/python/importing-modules.html" class="sidebar-link">Importing modules</a></li><li><a href="/python/difference-between-module-and-package.html" class="sidebar-link">Difference between Module and Package</a></li><li><a href="/python/math-module.html" class="sidebar-link">Math Module</a></li><li><a href="/python/complex-math.html" class="sidebar-link">Complex math</a></li><li><a href="/python/collections-module.html" class="sidebar-link">Collections module</a></li><li><a href="/python/operator-module.html" class="sidebar-link">Operator module</a></li><li><a href="/python/json-module.html" class="sidebar-link">JSON Module</a></li><li><a href="/python/sqlite3-module.html" class="sidebar-link">Sqlite3 Module</a></li><li><a href="/python/the-os-module.html" class="sidebar-link">The os Module</a></li><li><a href="/python/the-locale-module.html" class="sidebar-link">The locale Module</a></li><li><a href="/python/itertools-module.html" class="sidebar-link">Itertools Module</a></li><li><a href="/python/asyncio-module.html" class="sidebar-link">Asyncio Module</a></li><li><a href="/python/random-module.html" class="sidebar-link">Random module</a></li><li><a href="/python/functools-module.html" class="sidebar-link">Functools Module</a></li><li><a href="/python/the-dis-module.html" class="sidebar-link">The dis module</a></li><li><a href="/python/the-base64-module.html" class="sidebar-link">The base64 Module</a></li><li><a href="/python/queue-module.html" class="sidebar-link">Queue Module</a></li><li><a href="/python/deque-module.html" class="sidebar-link">Deque Module</a></li><li><a href="/python/webbrowser-module.html" class="sidebar-link">Webbrowser Module</a></li><li><a href="/python/tkinter.html" class="sidebar-link">tkinter</a></li><li><a href="/python/pyautogui-module.html" class="sidebar-link">pyautogui module</a></li><li><a href="/python/indexing-and-slicing.html" class="sidebar-link">Indexing and Slicing</a></li><li><a href="/python/plotting-with-matplotlib.html" class="sidebar-link">Plotting with Matplotlib</a></li><li><a href="/python/graph-tool.html" class="sidebar-link">graph-tool</a></li><li><a href="/python/generators.html" class="sidebar-link">Generators</a></li><li><a href="/python/reduce.html" class="sidebar-link">Reduce</a></li><li><a href="/python/map-function.html" class="sidebar-link">Map Function</a></li><li><a href="/python/exponentiation.html" class="sidebar-link">Exponentiation</a></li><li><a href="/python/searching.html" class="sidebar-link">Searching</a></li><li><a href="/python/sorting-minimum-and-maximum.html" class="sidebar-link">Sorting, Minimum and Maximum</a></li><li><a href="/python/counting.html" class="sidebar-link">Counting</a></li><li><a href="/python/the-print-function.html" class="sidebar-link">The Print Function</a></li><li><a href="/python/regular-expressions-regex.html" class="sidebar-link">Regular Expressions (Regex)</a></li><li><a href="/python/copying-data.html" class="sidebar-link">Copying data</a></li><li><a href="/python/context-managers-with-statement.html" class="sidebar-link">Context Managers (“with” Statement)</a></li><li><a href="/python/the-name-special-variable.html" class="sidebar-link">The _name_ special variable</a></li><li><a href="/python/checking-path-existence-and-permissions.html" class="sidebar-link">Checking Path Existence and Permissions</a></li><li><a href="/python/creating-python-packages.html" class="sidebar-link">Creating Python packages</a></li><li><a href="/python/usage-of-pip-module-pypi-package-manager.html" class="sidebar-link">Usage of "pip" module: PyPI Package Manager</a></li><li><a href="/python/pip-pypi-package-manager.html" class="sidebar-link">pip: PyPI Package Manager</a></li><li><a href="/python/parsing-command-line-arguments.html" class="sidebar-link">Parsing Command Line arguments</a></li><li><a href="/python/subprocess-library.html" class="sidebar-link">Subprocess Library</a></li><li><a href="/python/setup-py.html" class="sidebar-link">setup.py</a></li><li><a href="/python/recursion.html" class="sidebar-link">Recursion</a></li><li><a href="/python/type-hints.html" class="sidebar-link">Type Hints</a></li><li><a href="/python/exceptions.html" class="sidebar-link">Exceptions</a></li><li><a href="/python/raise-custom-errors-exceptions.html" class="sidebar-link">Raise Custom Errors / Exceptions</a></li><li><a href="/python/commonwealth-exceptions.html" class="sidebar-link">Commonwealth Exceptions</a></li><li><a href="/python/urllib.html" class="sidebar-link">urllib</a></li><li><a href="/python/web-scraping-with-python.html" class="sidebar-link">Web scraping with Python</a></li><li><a href="/python/html-parsing.html" class="sidebar-link">HTML Parsing</a></li><li><a href="/python/manipulating-xml.html" class="sidebar-link">Manipulating XML</a></li><li><a href="/python/python-requests-post.html" class="sidebar-link">Python Requests Post</a></li><li><a href="/python/distribution.html" class="sidebar-link">Distribution</a></li><li><a href="/python/property-objects.html" class="sidebar-link">Property Objects</a></li><li><a href="/python/overloading.html" class="sidebar-link">Overloading</a></li><li><a href="/python/polymorphism.html" class="sidebar-link">Polymorphism</a></li><li><a href="/python/method-overriding.html" class="sidebar-link">Method Overriding</a></li><li><a href="/python/user-defined-methods.html" class="sidebar-link">User-Defined Methods</a></li><li><a href="/python/string-representations-of-class-instances-str-and-repr-methods.html" class="sidebar-link">String representations of class instances: _str and repr_ methods</a></li><li><a href="/python/debugging.html" class="sidebar-link">Debugging</a></li><li><a href="/python/reading-and-writing-csv.html" class="sidebar-link">Reading and Writing CSV</a></li><li><a href="/python/writing-to-csv-from-string-or-list.html" class="sidebar-link">Writing to CSV from String or List</a></li><li><a href="/python/dynamic-code-execution-with-exec-and-eval.html" class="sidebar-link">Dynamic code execution with exec and eval</a></li><li><a href="/python/pyinstaller-distributing-python-code.html" class="sidebar-link">PyInstaller - Distributing Python Code</a></li><li><a href="/python/data-visualization-with-python.html" class="sidebar-link">Data Visualization with Python</a></li><li><a href="/python/the-interpreter-command-line-console.html" class="sidebar-link">The Interpreter (Command Line Console)</a></li><li><a href="/python/args-and-kwargs.html" class="sidebar-link">args and *kwargs</a></li><li><a href="/python/garbage-collection.html" class="sidebar-link">Garbage Collection</a></li><li><a href="/python/pickle-data-serialisation.html" class="sidebar-link">Pickle data serialisation</a></li><li><a href="/python/binary-data.html" class="sidebar-link">Binary Data</a></li><li><a href="/python/idioms.html" class="sidebar-link">Idioms</a></li><li><a href="/python/data-serialization.html" class="sidebar-link">Data Serialization</a></li><li><a href="/python/multiprocessing.html" class="sidebar-link">Multiprocessing</a></li><li><a href="/python/multithreading.html" class="sidebar-link">Multithreading</a></li><li><a href="/python/processes-and-threads.html" class="sidebar-link">Processes and Threads</a></li><li><a href="/python/python-concurrency.html" class="sidebar-link">Python concurrency</a></li><li><a href="/python/parallel-computation.html" class="sidebar-link">Parallel computation</a></li><li><a href="/python/sockets.html" class="sidebar-link">Sockets</a></li><li><a href="/python/websockets.html" class="sidebar-link">Websockets</a></li><li><a href="/python/sockets-and-message-encryption-decryption-between-client-and-server.html" class="sidebar-link">Sockets And Message Encryption/Decryption Between Client and Server</a></li><li><a href="/python/python-networking.html" class="sidebar-link">Python Networking</a></li><li><a href="/python/python-http-server.html" class="sidebar-link">Python HTTP Server</a></li><li><a href="/python/flask.html" class="sidebar-link">Flask</a></li><li><a href="/python/introduction-to-rabbitmq-using-amqpstorm.html" class="sidebar-link">Introduction to RabbitMQ using AMQPStorm</a></li><li><a href="/python/descriptor.html" class="sidebar-link">Descriptor</a></li><li><a href="/python/tempfile-namedtemporaryfile.html" class="sidebar-link">tempfile NamedTemporaryFile</a></li><li><a href="/python/input-subset-and-output-external-data-files-using-pandas.html" class="sidebar-link">Input, Subset and Output External Data Files using Pandas</a></li><li><a href="/python/unzipping-files.html" class="sidebar-link">Unzipping Files</a></li><li><a href="/python/working-with-zip-archives.html" class="sidebar-link">Working with ZIP archives</a></li><li><a href="/python/getting-start-with-gzip.html" class="sidebar-link">getting start with GZip</a></li><li><a href="/python/stack.html" class="sidebar-link">Stack</a></li><li><a href="/python/working-around-the-global-interpreter-lock-gil.html" class="sidebar-link">Working around the Global Interpreter Lock (GIL)</a></li><li><a href="/python/deployment.html" class="sidebar-link">Deployment</a></li><li><a href="/python/logging.html" class="sidebar-link">Logging</a></li><li><a href="/python/web-server-gateway-interface-wsgi.html" class="sidebar-link">Web Server Gateway Interface (WSGI)</a></li><li><a href="/python/python-server-sent-events.html" class="sidebar-link">Python Server Sent Events</a></li><li><a href="/python/alternatives-to-switch-statement-from-other-languages.html" class="sidebar-link">Alternatives to switch statement from other languages</a></li><li><a href="/python/list-destructuring-aka-packing-and-unpacking.html" class="sidebar-link">List destructuring (aka packing and unpacking)</a></li><li><a href="/python/accessing-python-source-code-and-bytecode.html" class="sidebar-link">Accessing Python source code and bytecode</a></li><li><a href="/python/mixins.html" class="sidebar-link">Mixins</a></li><li><a href="/python/attribute-access.html" class="sidebar-link">Attribute Access</a></li><li><a href="/python/arcpy.html" class="sidebar-link">ArcPy</a></li><li><a href="/python/abstract-base-classes-abc.html" class="sidebar-link">Abstract Base Classes (abc)</a></li><li><a href="/python/plugin-and-extension-classes.html" class="sidebar-link">Plugin and Extension Classes</a></li><li><a href="/python/immutable-datatypes-int-float-str-tuple-and-frozensets.html" class="sidebar-link">Immutable datatypes(int, float, str, tuple and frozensets)</a></li><li><a href="/python/incompatibilities-moving-from-python-2-to-python-3.html" class="sidebar-link">Incompatibilities moving from Python 2 to Python 3</a></li><li><a href="/python/2to3-tool.html" class="sidebar-link">2to3 tool</a></li><li><a href="/python/non-official-python-implementations.html" class="sidebar-link">Non-official Python implementations</a></li><li><a href="/python/abstract-syntax-tree.html" class="sidebar-link">Abstract syntax tree</a></li><li><a href="/python/unicode-and-bytes.html" class="sidebar-link">Unicode and bytes</a></li><li><a href="/python/python-serial-communication-pyserial.html" class="sidebar-link">Python Serial Communication (pyserial)</a></li><li><a href="/python/neo4j-and-cypher-using-py2neo.html" class="sidebar-link">Neo4j and Cypher using Py2Neo</a></li><li><a href="/python/basic-curses-with-python.html" class="sidebar-link">Basic Curses with Python</a></li><li><a href="/python/templates-in-python.html" class="sidebar-link">Templates in python</a></li><li><a href="/python/pillow.html" class="sidebar-link">Pillow</a></li><li><a href="/python/the-pass-statement.html" class="sidebar-link">The pass statement</a></li><li><a href="/python/cli-subcommands-with-precise-help-output.html" class="sidebar-link">CLI subcommands with precise help output</a></li><li><a href="/python/database-access.html" class="sidebar-link">Database Access</a></li><li><a href="/python/connecting-python-to-sql-server.html" class="sidebar-link">Connecting Python to SQL Server</a></li><li><a href="/python/postgresql.html" class="sidebar-link">PostgreSQL</a></li><li><a href="/python/python-and-excel.html" class="sidebar-link">Python and Excel</a></li><li><a href="/python/turtle-graphics.html" class="sidebar-link">Turtle Graphics</a></li><li><a href="/python/python-persistence.html" class="sidebar-link">Python Persistence</a></li><li><a href="/python/design-patterns.html" class="sidebar-link">Design Patterns</a></li><li><a href="/python/hashlib.html" class="sidebar-link">hashlib</a></li><li><a href="/python/creating-a-windows-service-using-python.html" class="sidebar-link">Creating a Windows service using Python</a></li><li><a href="/python/mutable-vs-immutable-and-hashable-in-python.html" class="sidebar-link">Mutable vs Immutable (and Hashable) in Python</a></li><li><a href="/python/configparser.html" class="sidebar-link">configparser</a></li><li><a href="/python/optical-character-recognition.html" class="sidebar-link">Optical Character Recognition</a></li><li><a href="/python/virtual-environments.html" class="sidebar-link">Virtual environments</a></li><li><a href="/python/python-virtual-environment-virtualenv.html" class="sidebar-link">Python Virtual Environment - virtualenv</a></li><li><a href="/python/virtual-environment-with-virtualenvwrapper.html" class="sidebar-link">virtual environment with virtualenvwrapper</a></li><li><a href="/python/create-virtual-environment-with-virtualenvwrapper-in-windows.html" class="sidebar-link">Create virtual environment with virtualenvwrapper in windows</a></li><li><a href="/python/sys.html" class="sidebar-link">sys</a></li><li><a href="/python/chempy-python-package.html" class="sidebar-link">ChemPy - python package</a></li><li><a href="/python/pygame.html" class="sidebar-link">pygame</a></li><li><a href="/python/pyglet.html" class="sidebar-link">Pyglet</a></li><li><a href="/python/audio.html" class="sidebar-link">Audio</a></li><li><a href="/python/pyaudio.html" class="sidebar-link">pyaudio</a></li><li><a href="/python/shelve.html" class="sidebar-link">shelve</a></li><li><a href="/python/iot-programming-with-python-and-raspberry-pi.html" class="sidebar-link">IoT Programming with Python and Raspberry PI</a></li><li><a href="/python/kivy-cross-platform-python-framework-for-nui-development.html" class="sidebar-link">kivy - Cross-platform Python Framework for NUI Development</a></li><li><a href="/python/pandas-transform-preform-operations-on-groups-and-concatenate-the-results.html" class="sidebar-link">Pandas Transform: Preform operations on groups and concatenate the results</a></li><li><a href="/python/similarities-in-syntax-differences-in-meaning-python-vs-javascript.html" class="sidebar-link">Similarities in syntax, Differences in meaning: Python vs. JavaScript</a></li><li><a href="/python/call-python-from-c.html" class="sidebar-link">Call Python from C#</a></li><li><a href="/python/ctypes.html" class="sidebar-link">ctypes</a></li><li><a href="/python/writing-extensions.html" class="sidebar-link">Writing extensions</a></li><li><a href="/python/python-lex-yacc.html" class="sidebar-link">Python Lex-Yacc</a></li><li><a href="/python/unit-testing.html" class="sidebar-link">Unit Testing</a></li><li><a href="/python/py-test.html" class="sidebar-link">py.test</a></li><li><a href="/python/profiling.html" class="sidebar-link">Profiling</a></li><li><a href="/python/python-speed-of-program.html" class="sidebar-link">Python speed of program</a></li><li><a href="/python/performance-optimization.html" class="sidebar-link">Performance optimization</a></li><li><a href="/python/security-and-cryptography.html" class="sidebar-link">Security and Cryptography</a></li><li><a href="/python/secure-shell-connection-in-python.html" class="sidebar-link">Secure Shell Connection in Python</a></li><li><a href="/python/python-anti-patterns.html" class="sidebar-link">Python Anti-Patterns</a></li><li><a href="/python/common-pitfalls.html" class="sidebar-link">Common Pitfalls</a></li><li><a href="/python/hidden-features.html" class="sidebar-link">Hidden Features</a></li><li><a href="/python/date-formatting.html" class="sidebar-link">Date Formatting</a></li><li><a href="/python/ijson.html" class="sidebar-link">ijson</a></li><li><a href="/python/django.html" class="sidebar-link">Django</a></li><li><a href="/python/code-blocks-execution-frames-and-namespaces.html" class="sidebar-link">Code blocks, execution frames, and namespaces</a></li><li><a href="/python/contributors.html" class="sidebar-link">The Contributors</a></li></ul></section></li></ul> </aside> <main class="page"> <div class="theme-default-content content__default"><h1 id="groupby"><a href="#groupby" class="header-anchor">#</a> groupby()</h1> <p>In Python, the <code>itertools.groupby()</code> method allows developers to group values of an iterable class based on a specified property into another iterable set of values.</p> <h2 id="example-4"><a href="#example-4" class="header-anchor">#</a> Example 4</h2> <p>In this example we see what happens when we use different types of iterable.</p> <div class="language-py extra-class"><pre class="language-py"><code>things <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">(</span><span class="token string">"animal"</span><span class="token punctuation">,</span> <span class="token string">"bear"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">"animal"</span><span class="token punctuation">,</span> <span class="token string">"duck"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">"plant"</span><span class="token punctuation">,</span> <span class="token string">"cactus"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">"vehicle"</span><span class="token punctuation">,</span> <span class="token string">"harley"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> \
<span class="token punctuation">(</span><span class="token string">"vehicle"</span><span class="token punctuation">,</span> <span class="token string">"speed boat"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">"vehicle"</span><span class="token punctuation">,</span> <span class="token string">"school bus"</span><span class="token punctuation">)</span><span class="token punctuation">]</span>
dic <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
f <span class="token operator">=</span> <span class="token keyword">lambda</span> x<span class="token punctuation">:</span> x<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span>
<span class="token keyword">for</span> key<span class="token punctuation">,</span> group <span class="token keyword">in</span> groupby<span class="token punctuation">(</span><span class="token builtin">sorted</span><span class="token punctuation">(</span>things<span class="token punctuation">,</span> key<span class="token operator">=</span>f<span class="token punctuation">)</span><span class="token punctuation">,</span> f<span class="token punctuation">)</span><span class="token punctuation">:</span>
dic<span class="token punctuation">[</span>key<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token builtin">list</span><span class="token punctuation">(</span>group<span class="token punctuation">)</span>
dic
</code></pre></div><p>Results in</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token punctuation">{</span><span class="token string">'animal'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">(</span><span class="token string">'animal'</span><span class="token punctuation">,</span> <span class="token string">'bear'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">'animal'</span><span class="token punctuation">,</span> <span class="token string">'duck'</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'plant'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">(</span><span class="token string">'plant'</span><span class="token punctuation">,</span> <span class="token string">'cactus'</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'vehicle'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">(</span><span class="token string">'vehicle'</span><span class="token punctuation">,</span> <span class="token string">'harley'</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token punctuation">(</span><span class="token string">'vehicle'</span><span class="token punctuation">,</span> <span class="token string">'speed boat'</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token punctuation">(</span><span class="token string">'vehicle'</span><span class="token punctuation">,</span> <span class="token string">'school bus'</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
</code></pre></div><p>This example below is essentially the same as the one above it. The only difference is that I have changed all the tuples to lists.</p> <div class="language-py extra-class"><pre class="language-py"><code>things <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token string">"animal"</span><span class="token punctuation">,</span> <span class="token string">"bear"</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token string">"animal"</span><span class="token punctuation">,</span> <span class="token string">"duck"</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token string">"vehicle"</span><span class="token punctuation">,</span> <span class="token string">"harley"</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token string">"plant"</span><span class="token punctuation">,</span> <span class="token string">"cactus"</span><span class="token punctuation">]</span><span class="token punctuation">,</span> \
<span class="token punctuation">[</span><span class="token string">"vehicle"</span><span class="token punctuation">,</span> <span class="token string">"speed boat"</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token string">"vehicle"</span><span class="token punctuation">,</span> <span class="token string">"school bus"</span><span class="token punctuation">]</span><span class="token punctuation">]</span>
dic <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
f <span class="token operator">=</span> <span class="token keyword">lambda</span> x<span class="token punctuation">:</span> x<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span>
<span class="token keyword">for</span> key<span class="token punctuation">,</span> group <span class="token keyword">in</span> groupby<span class="token punctuation">(</span><span class="token builtin">sorted</span><span class="token punctuation">(</span>things<span class="token punctuation">,</span> key<span class="token operator">=</span>f<span class="token punctuation">)</span><span class="token punctuation">,</span> f<span class="token punctuation">)</span><span class="token punctuation">:</span>
dic<span class="token punctuation">[</span>key<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token builtin">list</span><span class="token punctuation">(</span>group<span class="token punctuation">)</span>
dic
</code></pre></div><p>Results</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token punctuation">{</span><span class="token string">'animal'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token string">'animal'</span><span class="token punctuation">,</span> <span class="token string">'bear'</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token string">'animal'</span><span class="token punctuation">,</span> <span class="token string">'duck'</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'plant'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token string">'plant'</span><span class="token punctuation">,</span> <span class="token string">'cactus'</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'vehicle'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token string">'vehicle'</span><span class="token punctuation">,</span> <span class="token string">'harley'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token punctuation">[</span><span class="token string">'vehicle'</span><span class="token punctuation">,</span> <span class="token string">'speed boat'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token punctuation">[</span><span class="token string">'vehicle'</span><span class="token punctuation">,</span> <span class="token string">'school bus'</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
</code></pre></div><h2 id="example-2"><a href="#example-2" class="header-anchor">#</a> Example 2</h2> <p>This example illustrates how the default key is chosen if we do not specify any</p> <div class="language-py extra-class"><pre class="language-py"><code>c <span class="token operator">=</span> groupby<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">'goat'</span><span class="token punctuation">,</span> <span class="token string">'dog'</span><span class="token punctuation">,</span> <span class="token string">'cow'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">11</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">'persons'</span><span class="token punctuation">,</span> <span class="token string">'man'</span><span class="token punctuation">,</span> <span class="token string">'woman'</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
dic <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
<span class="token keyword">for</span> k<span class="token punctuation">,</span> v <span class="token keyword">in</span> c<span class="token punctuation">:</span>
dic<span class="token punctuation">[</span>k<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token builtin">list</span><span class="token punctuation">(</span>v<span class="token punctuation">)</span>
dic
</code></pre></div><p>Results in</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token number">2</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token number">3</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token punctuation">(</span><span class="token string">'persons'</span><span class="token punctuation">,</span> <span class="token string">'man'</span><span class="token punctuation">,</span> <span class="token string">'woman'</span><span class="token punctuation">)</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">(</span><span class="token string">'persons'</span><span class="token punctuation">,</span> <span class="token string">'man'</span><span class="token punctuation">,</span> <span class="token string">'woman'</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'cow'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'cow'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'dog'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'dog'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token number">10</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token number">10</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token number">11</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token number">11</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'goat'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'goat'</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
</code></pre></div><p>Notice here that the tuple as a whole counts as one key in this list</p> <h2 id="example-3"><a href="#example-3" class="header-anchor">#</a> Example 3</h2> <p>Notice in this example that mulato and camel don't show up in our result. Only the last element with the specified key shows up. The last result for c actually wipes out two previous results. But watch the new version where I have the data sorted first on same key.</p> <div class="language-py extra-class"><pre class="language-py"><code>list_things <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'goat'</span><span class="token punctuation">,</span> <span class="token string">'dog'</span><span class="token punctuation">,</span> <span class="token string">'donkey'</span><span class="token punctuation">,</span> <span class="token string">'mulato'</span><span class="token punctuation">,</span> <span class="token string">'cow'</span><span class="token punctuation">,</span> <span class="token string">'cat'</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">'persons'</span><span class="token punctuation">,</span> <span class="token string">'man'</span><span class="token punctuation">,</span> <span class="token string">'woman'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> \
<span class="token string">'wombat'</span><span class="token punctuation">,</span> <span class="token string">'mongoose'</span><span class="token punctuation">,</span> <span class="token string">'malloo'</span><span class="token punctuation">,</span> <span class="token string">'camel'</span><span class="token punctuation">]</span>
c <span class="token operator">=</span> groupby<span class="token punctuation">(</span>list_things<span class="token punctuation">,</span> key<span class="token operator">=</span><span class="token keyword">lambda</span> x<span class="token punctuation">:</span> x<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
dic <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
<span class="token keyword">for</span> k<span class="token punctuation">,</span> v <span class="token keyword">in</span> c<span class="token punctuation">:</span>
dic<span class="token punctuation">[</span>k<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token builtin">list</span><span class="token punctuation">(</span>v<span class="token punctuation">)</span>
dic
</code></pre></div><p>Results in</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token punctuation">{</span><span class="token string">'c'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'camel'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'d'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'dog'</span><span class="token punctuation">,</span> <span class="token string">'donkey'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'g'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'goat'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'m'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'mongoose'</span><span class="token punctuation">,</span> <span class="token string">'malloo'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'persons'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">(</span><span class="token string">'persons'</span><span class="token punctuation">,</span> <span class="token string">'man'</span><span class="token punctuation">,</span> <span class="token string">'woman'</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'w'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'wombat'</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
</code></pre></div><p>Sorted Version</p> <div class="language-py extra-class"><pre class="language-py"><code>list_things <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'goat'</span><span class="token punctuation">,</span> <span class="token string">'dog'</span><span class="token punctuation">,</span> <span class="token string">'donkey'</span><span class="token punctuation">,</span> <span class="token string">'mulato'</span><span class="token punctuation">,</span> <span class="token string">'cow'</span><span class="token punctuation">,</span> <span class="token string">'cat'</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">'persons'</span><span class="token punctuation">,</span> <span class="token string">'man'</span><span class="token punctuation">,</span> <span class="token string">'woman'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> \
<span class="token string">'wombat'</span><span class="token punctuation">,</span> <span class="token string">'mongoose'</span><span class="token punctuation">,</span> <span class="token string">'malloo'</span><span class="token punctuation">,</span> <span class="token string">'camel'</span><span class="token punctuation">]</span>
sorted_list <span class="token operator">=</span> <span class="token builtin">sorted</span><span class="token punctuation">(</span>list_things<span class="token punctuation">,</span> key <span class="token operator">=</span> <span class="token keyword">lambda</span> x<span class="token punctuation">:</span> x<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>sorted_list<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
c <span class="token operator">=</span> groupby<span class="token punctuation">(</span>sorted_list<span class="token punctuation">,</span> key<span class="token operator">=</span><span class="token keyword">lambda</span> x<span class="token punctuation">:</span> x<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
dic <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
<span class="token keyword">for</span> k<span class="token punctuation">,</span> v <span class="token keyword">in</span> c<span class="token punctuation">:</span>
dic<span class="token punctuation">[</span>k<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token builtin">list</span><span class="token punctuation">(</span>v<span class="token punctuation">)</span>
dic
</code></pre></div><p>Results in</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token punctuation">[</span><span class="token string">'cow'</span><span class="token punctuation">,</span> <span class="token string">'cat'</span><span class="token punctuation">,</span> <span class="token string">'camel'</span><span class="token punctuation">,</span> <span class="token string">'dog'</span><span class="token punctuation">,</span> <span class="token string">'donkey'</span><span class="token punctuation">,</span> <span class="token string">'goat'</span><span class="token punctuation">,</span> <span class="token string">'mulato'</span><span class="token punctuation">,</span> <span class="token string">'mongoose'</span><span class="token punctuation">,</span> <span class="token string">'malloo'</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token string">'persons'</span><span class="token punctuation">,</span> <span class="token string">'man'</span><span class="token punctuation">,</span> <span class="token string">'woman'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token string">'wombat'</span><span class="token punctuation">]</span>
<span class="token punctuation">{</span><span class="token string">'c'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'cow'</span><span class="token punctuation">,</span> <span class="token string">'cat'</span><span class="token punctuation">,</span> <span class="token string">'camel'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'d'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'dog'</span><span class="token punctuation">,</span> <span class="token string">'donkey'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'g'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'goat'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'m'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'mulato'</span><span class="token punctuation">,</span> <span class="token string">'mongoose'</span><span class="token punctuation">,</span> <span class="token string">'malloo'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'persons'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token punctuation">(</span><span class="token string">'persons'</span><span class="token punctuation">,</span> <span class="token string">'man'</span><span class="token punctuation">,</span> <span class="token string">'woman'</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'w'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'wombat'</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
</code></pre></div><h2 id="example-1"><a href="#example-1" class="header-anchor">#</a> Example 1</h2> <p>Say you have the string</p> <div class="language-py extra-class"><pre class="language-py"><code>s <span class="token operator">=</span> <span class="token string">'AAAABBBCCDAABBB'</span>
</code></pre></div><p>and you would like to split it so all the 'A's are in one list and so with all the 'B's and 'C', etc.
You could do something like this</p> <div class="language-py extra-class"><pre class="language-py"><code>s <span class="token operator">=</span> <span class="token string">'AAAABBBCCDAABBB'</span>
s_dict <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
<span class="token keyword">for</span> i <span class="token keyword">in</span> s<span class="token punctuation">:</span>
<span class="token keyword">if</span> i <span class="token keyword">not</span> <span class="token keyword">in</span> s_dict<span class="token punctuation">.</span>keys<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">:</span>
s_dict<span class="token punctuation">[</span>i<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">[</span>i<span class="token punctuation">]</span>
<span class="token keyword">else</span><span class="token punctuation">:</span>
s_dict<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span>append<span class="token punctuation">(</span>i<span class="token punctuation">)</span>
s_dict
</code></pre></div><p>Results in</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token punctuation">{</span><span class="token string">'A'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'B'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'C'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'C'</span><span class="token punctuation">,</span> <span class="token string">'C'</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token string">'D'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'D'</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
</code></pre></div><p>But for large data set you would be building up these items in memory. This is where groupby() comes in</p> <p>We could get the same result in a more efficient manner by doing the following</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token comment"># note that we get a {key : value} pair for iterating over the items just like in python dictionary</span>
<span class="token keyword">from</span> itertools <span class="token keyword">import</span> groupby
s <span class="token operator">=</span> <span class="token string">'AAAABBBCCDAABBB'</span>
c <span class="token operator">=</span> groupby<span class="token punctuation">(</span>s<span class="token punctuation">)</span>
dic <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
<span class="token keyword">for</span> k<span class="token punctuation">,</span> v <span class="token keyword">in</span> c<span class="token punctuation">:</span>
dic<span class="token punctuation">[</span>k<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token builtin">list</span><span class="token punctuation">(</span>v<span class="token punctuation">)</span>
dic
</code></pre></div><p>Results in</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token punctuation">{</span><span class="token string">'A'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token string">'C'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'C'</span><span class="token punctuation">,</span> <span class="token string">'C'</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token string">'D'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'D'</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
</code></pre></div><p>Notice that the number of 'A's in the result when we used group by is less than the actual number of 'A's in the original string. We can avoid that loss of information by sorting the items in s before passing it to c as shown below</p> <div class="language-py extra-class"><pre class="language-py"><code>c <span class="token operator">=</span> groupby<span class="token punctuation">(</span><span class="token builtin">sorted</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span><span class="token punctuation">)</span>
dic <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
<span class="token keyword">for</span> k<span class="token punctuation">,</span> v <span class="token keyword">in</span> c<span class="token punctuation">:</span>
dic<span class="token punctuation">[</span>k<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token builtin">list</span><span class="token punctuation">(</span>v<span class="token punctuation">)</span>
dic
</code></pre></div><p>Results in</p> <div class="language-py extra-class"><pre class="language-py"><code><span class="token punctuation">{</span><span class="token string">'A'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token string">'C'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'C'</span><span class="token punctuation">,</span> <span class="token string">'C'</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token string">'D'</span><span class="token punctuation">:</span> <span class="token punctuation">[</span><span class="token string">'D'</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
</code></pre></div><p>Now we have all our 'A's.</p> <h4 id="syntax"><a href="#syntax" class="header-anchor">#</a> Syntax</h4> <ul><li>itertools.groupby(iterable, key=None or some function)</li></ul> <h4 id="parameters"><a href="#parameters" class="header-anchor">#</a> Parameters</h4> <table><thead><tr><th>Parameter</th> <th>Details</th></tr></thead> <tbody><tr><td>iterable</td> <td>Any python iterable</td></tr> <tr><td>key</td> <td>Function(criteria) on which to group the iterable</td></tr></tbody></table> <h4 id="remarks"><a href="#remarks" class="header-anchor">#</a> Remarks</h4> <p>groupby() is tricky but a general rule to keep in mind when using it is this:</p> <p><strong>Always sort the items you want to group with the same key you want to use for grouping</strong></p> <p>It is recommended that the reader take a look at the documentation <a href="https://docs.python.org/3/library/itertools.html#itertools.groupby" target="_blank" rel="noopener noreferrer">here<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> and see how it is explained using a class definition.</p></div> <footer class="page-edit"><div class="edit-link"><a href="https://github.com/devtut/generate/edit/master/docs/python/groupby.md" target="_blank" rel="noopener noreferrer">Edit this page on GitHub</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----></footer> <div class="page-nav"><p class="inner"><span class="prev">
←
<a href="/python/list-slicing-selecting-parts-of-lists.html" class="prev">
List slicing (selecting parts of lists)
</a></span> <span class="next"><a href="/python/linked-lists.html">
Linked lists
</a>
→
</span></p></div> </main></div><div class="global-ui"><!----></div></div>
<script src="/assets/js/app.1779e102.js" defer></script><script src="/assets/js/3.2cfa8016.js" defer></script><script src="/assets/js/2715.71e34515.js" defer></script>
</body>
</html>