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<div class="slide" id="slide-1">

<section class="slide-content"><h1 id="python-basics">Python Basics</h1>

<h2 id="a-quick-primer-on-the-scripting-language-">A quick primer on the scripting language.</h2>

<p><em>Generated using <a href="https://github.com/jdan/cleaver">cleaver</a></em></p>

</div>

<div class="slide hidden" id="slide-2">

<section class="slide-content"><ul>

<li>Introduction to Python</li>

<li>Control Structures</li>

<li>Basic Data Types</li>

<li>Advanced Data Types</li>

<li>Dictionaries</li>

<li>Functions</li>

<li>Exception Handling</li>

<li>Classes</li>

<li>Files</li>

<li>Larger Programs</li>

<li>Pattern Matching</li>

</div>

<div class="slide hidden" id="slide-3">

<section class="slide-content"><h3 id="introduction-to-python">Introduction to Python</h3>

<li>General purpose high level scripting language:</li>

<li>Emphasis placed on<ul>

<li>Human Readability.</li>

<li>Self describing code.</li>

<p><em>from PEP-20 - The Zen of Python</em>:</p>

<pre><code> Beautiful is better than ugly

Explicit is better than implicit

Simple is better than complex

Complex is better than complicated

Readability counts</code></pre>

</div>

<div class="slide hidden" id="slide-4">

<section class="slide-content"><h3 id="introduction-to-python-hello-world-">Introduction to Python - <em>Hello World</em></h3>

<p>Python can be run in two ways, either in <strong>The Python Interpreter</strong>:</p>

<p><em>hello.py</em>:</p>

<pre><code class="lang-python">print(<span class="hljs-string">'Hello World!'</span>)</code></pre>

<pre><code class="lang-bash">&gt; python hello.py

Hello World!</code></pre>

<p>or in an <em>Interactive shell</em>:</p>

<pre><code class="lang-bash">&gt; python

Python 2.7.9 (default, May 1 2015, 19:04:44)

[GCC 4.2.1 Compatible Apple LLVM 6.1.0 (clang-602.0.49)] on darwin

Type <span class="hljs-string">"help"</span>, <span class="hljs-string">"copyright"</span>, <span class="hljs-string">"credits"</span> or <span class="hljs-string">"license"</span> <span class="hljs-keyword">for</span> more information.

&gt;&gt;&gt; <span class="hljs-built_in">print</span>(<span class="hljs-string">"Hello World!"</span>)

Hello World!

&gt;&gt;&gt; <span class="hljs-built_in">exit</span>()</code></pre>

<p><strong> Try doing the following in an interactive shell</strong>:</p>

<pre><code class="lang-python"><span class="hljs-keyword">import</span> this</code></pre>

</div>

<div class="slide hidden" id="slide-5">

<section class="slide-content"><h3 id="basic-data-types">Basic Data Types</h3>

<li>Everything is an object.<ul>

<li>Interpreter can be left to decide what a variable is.</li>

<li>Explicit casts are available (int(), str() etc) but are not recommended.</li>

<p><em>variables.py</em></p>

<pre><code class="lang-python">i = <span class="hljs-number">2</span>

f = <span class="hljs-number">0.33</span>

s = <span class="hljs-string">"This is a string"</span>

print(s)

print(f * i)</code></pre>

<pre><code class="lang-bash">&gt; python variables.py

This is a string

0.66</code></pre>

</div>

<div class="slide hidden" id="slide-6">

<section class="slide-content"><h3 id="basic-data-types-string-ms-since-everything-s-an-object-strings-have-methods-for-manipiulation-anipulation-">Basic Data Types - <em>String Ms = &#39;Since everything\&#39;s an object, strings have methods for manipiulation&#39;anipulation</em></h3>

<p>Since everything is an object, strings have builtin methods for modification.</p>

<p><em>strings.py</em></p>

<pre><code class="lang-python">s = <span class="hljs-string">'Since everything\'s an object, strings have methods for manipiulation'</span>

print(s)

print(s.rstrip(<span class="hljs-string">'manipiulation'</span>))

print(s.upper())

print(s.lower())

print(s.swapcase())</code></pre>

<pre><code>&gt; python strings.py

Since everything&#39;s an object, strings have methods for manipiulation

Since everything&#39;s an object, strings have methods for

SINCE EVERYTHING&#39;S AN OBJECT, STRINGS HAVE METHODS FOR MANIPIULATION

since everything&#39;s an object, strings have methods for manipiulation

sINCE EVERYTHING&#39;S AN OBJECT, STRINGS HAVE METHODS FOR MANIPIULATION</code></pre>

</div>

<div class="slide hidden" id="slide-7">

<section class="slide-content"><h3 id="sequence-data-types-lists-">Sequence Data Types - <em>Lists</em></h3>

<li>As described, lists are a collection of objects.</li>

<li>Behave in the same way as c arrays, but with the benifits of being an object in themselves!</li>

<li>Lists are <strong>mutable</strong>.</li>

<li>Can be added to with .append() and concanated with .extend()</li>

<p><em>list.py</em></p>

<pre><code class="lang-python">list_1 = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>]

list_2 = [<span class="hljs-string">'a'</span>, <span class="hljs-string">'b'</span>, <span class="hljs-string">'c'</span>, <span class="hljs-string">'d'</span>]

list_specials = [[<span class="hljs-string">'a'</span>], (<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>), <span class="hljs-keyword">False</span>]

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(list_1, len(list_1)))

list_1.append(<span class="hljs-number">5</span>)

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(list_1, len(list_1)))

list_1.extend(list_2)

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(list_1, len(list_1)))

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(list_specials, len(list_specials)))</code></pre>

<pre><code>&gt; python list.py

[1, 2, 3, 4] is of length 4

[1, 2, 3, 4, 5] is of length 5

[1, 2, 3, 4, 5, &#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;] is of length 9

[[&#39;a&#39;], (1, 2, 3), False] is of length 3</code></pre>

</div>

<div class="slide hidden" id="slide-8">

<section class="slide-content"><h3 id="sequence-data-types-tuples-">Sequence Data Types - <em>Tuples</em></h3>

<li>Similar to lists except that they are <strong>immutable</strong>!</li>

<li>Cannot be modified once created.</li>

<li>Useful when returning more than one thing from <em>functions</em> (see later).</li>

<p><em>tuple.py</em></p>

<pre><code class="lang-python">x1 = ()

x2 = (<span class="hljs-number">1</span>,)

x3 = (<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>)

x4 = (<span class="hljs-number">1</span>, <span class="hljs-string">"mixed"</span>, <span class="hljs-number">2</span>, <span class="hljs-string">"tuple"</span>)

x5 = ((<span class="hljs-number">1</span>, <span class="hljs-number">2</span>), (<span class="hljs-number">3</span>, <span class="hljs-number">4</span>))

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(x1, len(x1)))

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(x2, len(x2)))

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(x3, len(x3)))

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(x4, len(x4)))

print(<span class="hljs-string">'{0} is of length {1}'</span>.format(x5, len(x5)))</code></pre>

<pre><code>&gt; python tuple.py

() is of length 0

(1,) is of length 1

(1, 2, 3) is of length 3

(1, &#39;mixed&#39;, 2, &#39;tuple&#39;) is of length 4

((1, 2), (3, 4)) is of length 2</code></pre>

</div>

<div class="slide hidden" id="slide-9">

<section class="slide-content"><h3 id="sequence-data-types-dictionaries-">Sequence Data Types - <strong>Dictionaries</strong></h3>

<li>Used to store <strong>key value pairs</strong>.</li>

<li>Not stored in any particular order, left up to interpreter to order when inserting/accessing.</li>

<li>Values can be accessed/updated by refering to dictionary&#39;s key.</li>

<p><em>dict.py</em></p>

<pre><code class="lang-python">d = {}

d[<span class="hljs-string">'name'</span>] = <span class="hljs-string">'Matt'</span>

d[<span class="hljs-string">'job'</span>] = <span class="hljs-string">'something or other'</span>

print(d)

print(d.keys())

print(<span class="hljs-string">'my name is{0}'</span>.format(d[<span class="hljs-string">'name'</span>]))

print(<span class="hljs-string">'and i do {0}'</span>.format(d[<span class="hljs-string">'job'</span>]))</code></pre>

<pre><code>&gt; python dict.py

{&#39;job&#39;: &#39;something or other&#39;, &#39;name&#39;: &#39;Matt&#39;}

[&#39;job&#39;, &#39;name&#39;]

my name is Matt

and i do something or other</code></pre>

</div>

<div class="slide hidden" id="slide-10">

<section class="slide-content"><h3 id="control-structures">Control Structures</h3>

<h4 id="if">IF</h4>

<p>Only execute statement(s) if condtion is met.</p>

<pre><code class="lang-python">x = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>]

<span class="hljs-keyword">if</span> len(x) &gt; <span class="hljs-number">0</span>:

print(<span class="hljs-string">'IF:{0}'</span>.format(x))</code></pre>

<h4 id="for">FOR</h4>

<p>Iterates through items in collection (set, list, tuple etc...)</p>

<pre><code class="lang-python"><span class="hljs-keyword">for</span> item <span class="hljs-keyword">in</span> x:

print(<span class="hljs-string">'FOR:{0}'</span>.format(item))</code></pre>

<h4 id="while">WHILE</h4>

<p>Keep executing statement(s) until condition is not met.</p>

<pre><code class="lang-python">y = []

i = <span class="hljs-number">0</span>

<span class="hljs-keyword">while</span> len(y) &lt; len(x):

i += <span class="hljs-number">1</span>

y.append(i)

print(<span class="hljs-string">'WHILE:{0}'</span>.format(y))</code></pre>

<pre><code>IF:[1, 2, 3]

FOR:1

FOR:2

FOR:3

WHILE:[1]

WHILE:[1, 2]

WHILE:[1, 2, 3]</code></pre>

</div>

<div class="slide hidden" id="slide-11">

<section class="slide-content"><h3 id="functions">Functions</h3>

<li>Used to logically seperate off common code.</li>

<li>Can return value(s) to calling function.</li>

<pre><code class="lang-python"><span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">add_up</span><span class="hljs-params">(num_list)</span>:</span>

x = <span class="hljs-number">0</span>

<span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> num_list:

x += i

<span class="hljs-keyword">return</span> x

<span class="hljs-comment"># our script starts running from here.</span>

nums = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>, <span class="hljs-number">6</span>]

print(<span class="hljs-string">'The sum of {0} is {1}'</span>.format(nums, add_up(nums)))</code></pre>

<pre><code>The sum of [1, 2, 3, 4, 5, 6] is 21</code></pre>

</div>

<div class="slide hidden" id="slide-12">

<section class="slide-content"><h3 id="exception-handling">Exception Handling</h3>

<li>Gracefully handle problems occuring in execution.</li>

<li>exceptions are signals sent from interpreter at time of problem.</li>

<li>Unless handled, they will cause a program to crash, displaying the exception.</li>

<pre><code class="lang-python">x = <span class="hljs-number">3</span>

print(x / <span class="hljs-number">0</span>)</code></pre>

<pre><code>&gt; python exception.py

Traceback (most recent call last):

File &quot;exception.py&quot;, line 2, in &lt;module&gt;

print(x / 0)

ZeroDivisionError: integer division or modulo by zero</code></pre>

<li>Exceptions can be used by wrapping code in try / except statements.</li>

<pre><code class="lang-python">x = <span class="hljs-number">3</span>

<span class="hljs-keyword">try</span>:

print(x / <span class="hljs-number">0</span>)

<span class="hljs-keyword">except</span> ZeroDivisionError:

print(<span class="hljs-string">"You're trying to print by zero, this isnt allowed!"</span>)</code></pre>

<pre><code>&gt; python exception.py

You&#39;re trying to print by zero, this isnt allowed!</code></pre>

</div>

<div class="slide hidden" id="slide-13">

<section class="slide-content"><h3 id="classes">Classes</h3>

<li>Used to group together variables/classes logically (usually into a model of something).</li>

<li>All the types we have been using are classes!</li>

<p><em>class.py</em></p>

<pre><code class="lang-python"><span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">TrainingGroup</span>:</span>

<span class="hljs-comment"># class members</span>

date = <span class="hljs-string">''</span>

participants = []

<span class="hljs-comment"># class methods</span>

<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__init__</span><span class="hljs-params">(self, date, participants)</span>:</span>

self.date = date

self.participants = participants

<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__str__</span><span class="hljs-params">(self)</span>:</span>

<span class="hljs-keyword">return</span> <span class="hljs-string">'{0} participants on {1}'</span>.format(len(self.participants), self.date)

<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">kick_member</span><span class="hljs-params">(self, idiot)</span>:</span>

new_members = []

<span class="hljs-keyword">for</span> member <span class="hljs-keyword">in</span> self.participants:

<span class="hljs-keyword">if</span> idiot != member:

new_members.append(member)

<span class="hljs-keyword">else</span>:

print(<span class="hljs-string">'kicking {0}'</span>.format(idiot))

self.participants = new_members

group = TrainingGroup(<span class="hljs-string">'2015-08-10'</span>, [<span class="hljs-string">'Tom'</span>, <span class="hljs-string">'Dick'</span>, <span class="hljs-string">'Harry'</span>])

print(group)

print(group.participants)

group.kick_member(<span class="hljs-string">'Dick'</span>)

print(group)

print(group.participants)</code></pre>

<pre><code>&gt; python class.py

3 participants on 2015-08-10

[&#39;Tom&#39;, &#39;Dick&#39;, &#39;Harry&#39;]

kicking Dick

2 participants on 2015-08-10

[&#39;Tom&#39;, &#39;Harry&#39;]</code></pre>

</div>

<div class="slide hidden" id="slide-14">

<section class="slide-content"><h3 id="files">Files</h3>

<p><em>file.py</em></p>

<pre><code class="lang-python">infile = open(<span class="hljs-string">'testfile.txt'</span>, <span class="hljs-string">'r'</span>) <span class="hljs-comment"># opened for reading only</span>

outfile = open(<span class="hljs-string">'file.output.txt'</span>, <span class="hljs-string">'w'</span>) <span class="hljs-comment"># opened for writing</span>

<span class="hljs-keyword">for</span> line <span class="hljs-keyword">in</span> infile.readlines():

outfile.write(line)</code></pre>

<pre><code>&gt; python file.py

&gt; cat file.output.txt

this

is

is

a

test

file</code></pre>

<p>Files can be opened in different <em>modes</em>:</p>

<th style="text-align:left"></th>

<th style="text-align:left"></th>

<td style="text-align:left">r</td>

<td style="text-align:left">Open text file for reading. The stream is positioned at the beginning of the file.</td>

<td style="text-align:left">r+</td>

<td style="text-align:left">Open for reading and writing. The stream is positioned at the beginning of the file.</td>

<td style="text-align:left">w</td>

<td style="text-align:left">Truncate file to zero length or create text file for writing. The stream is positioned at the beginning of the file.</td>

<td style="text-align:left">w+</td>

<td style="text-align:left">Open for reading and writing. The file is created if it does not exist, otherwise it is truncated. The stream is</td>

<td style="text-align:left"></td>

<td style="text-align:left">positioned at the beginning of the file.</td>

<td style="text-align:left">a</td>

<td style="text-align:left">Open for writing. The file is created if it does not exist. The stream is positioned at the end of the file.</td>

<td style="text-align:left"></td>

<td style="text-align:left">Subsequent writes to the file will always end up at the then current end of file.</td>

<td style="text-align:left">a+</td>

<td style="text-align:left">Open for reading and writing. The file is created if it does not exist. The stream is positioned at the end of the</td>

<td style="text-align:left"></td>

<td style="text-align:left">file. Subsequent writes to the file will always end up at the then current end of file.</td>

</div>

<div class="slide hidden" id="slide-15">

<section class="slide-content"><h3 id="larger-programs-using-modules-">Larger Programs - <em>Using Modules</em></h3>

<li>Large codebases can be broken up into seperate files.</li>

<li><em>Calling</em> functions calling functions from another file need to have <strong>imported</strong> them before use.</li>

<li>Good practice to cut down on <em>code replication</em>.</li>

<li>Importing a file causes <strong>all code in the file to be executed</strong>.<ul>

<li>Need to be wary of code not within a function</li>

<li>Can <em>guard</em> against this code by wrapping it in <code>if __name__ == &#39;__main__&#39;:</code></li>

<p><em>mymodule.py</em></p>

<pre><code class="lang-python"><span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">sum_numeric_list</span><span class="hljs-params">(nums)</span>:</span>

<span class="hljs-string">"""

Accepts a list of numeric values.

Returns the sum of the elements.

"""</span>

sum = <span class="hljs-number">0</span>

<span class="hljs-keyword">for</span> item <span class="hljs-keyword">in</span> nums:

sum += item

<span class="hljs-keyword">return</span> sum

<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">prune_dict</span><span class="hljs-params">(dict, keys_to_remove)</span>:</span>

<span class="hljs-string">"""

Accepts a dict to priune and a list of keys to remove.

Matching keys are deleted and rmainders returned.

"""</span>

pruned_dict = {}

<span class="hljs-keyword">for</span> key <span class="hljs-keyword">in</span> dict.keys():

<span class="hljs-keyword">if</span> key <span class="hljs-keyword">not</span> <span class="hljs-keyword">in</span> keys_to_remove:

pruned_dict[key] = dict[key]

<span class="hljs-keyword">return</span> pruned_dict

<span class="hljs-keyword">if</span> __name__ == <span class="hljs-string">'__main__'</span>:

test_ints = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>]

print(<span class="hljs-string">'The sum of {0} is {1}'</span>.format(test_ints, sum_numeric_list(test_ints)))

test_dict = {<span class="hljs-string">'Tom'</span>: <span class="hljs-string">'The First'</span>, <span class="hljs-string">'Dick'</span>: <span class="hljs-string">'The Second'</span>, <span class="hljs-string">'Harry'</span>: <span class="hljs-string">'The Third'</span>}