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Dictionary

1. Dictionary holds key:value pair

2. Values in a dictionary can be of any datatype and can be duplicated

3. keys can’t be repeated

4. Dictionary keys are case sensitive, same name but different cases of Key will be treated distinctly.

5. Dictionary is mutable

# Creating a Dictionary

Type 1 :

Dict = {1: 'Geeks', 2: 'For', 3: 'Geeks'}

# Creating a Dictionary with Mixed keys

Type 2 :

Dict = {'Name': 'Geeks', 1: [1, 2, 3, 4]}

# Creating an empty Dictionary

Type 3 :

Dict = {}

print("Empty Dictionary: ")

# Creating a Dictionary with dict() method

Type 4 :

Dict = dict({1: 'Geeks', 2: 'For', 3:'Geeks'})

# Creating a Dictionary with each item as a Pair

Type 5 :

Dict = dict([(1, 'Geeks'), (2, 'For')])

# Creating a Nested Dictionary

Dict = {1: 'Geeks', 2: 'For', 3:{'A' : 'Welcome', 'B' : 'To', 'C' : 'Geeks'}}

Adding one element at a time

Dict[2] = 'For'

Dict[3] = 1

# Adding set of values to a single Key

Dict['Value_set'] = 2, 3, 4

# Updating existing Key's Value

Dict[2] = 'Welcome'

# accessing a element using key

Dict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'}

print("Accessing a element using key:")

print(Dict['name'])

There is also a method called get() that will also help in acessing the element from a dictionary.

# Creating a Dictionary

Dict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'}

# accessing a element using get() method

print("Accessing a element using get:")

print(Dict.get(3))

o/p: Geeks

Nested dictionary

# Creating a Dictionary

>>> col = {'Dict1': {1: 'Geeks'}, 'Dict2': {'Name': 'For'}}

Accessing elements

>>> col['Dict1']

{1: 'Geeks'}

>>> col['Dict2']

{'Name': 'For'}

Accessing elements

>>> col

{'Dict1': {1: 'Geeks'}, 'Dict2': {'Name': 'For'}}

>>> col['Dict1']

{1: 'Geeks'}

>>> col['Dict1'][1]

'Geeks'

>>> col['Dict2']['Name']

'For'

copy() :They copy() method returns a shallow copy of the dictionary.

clear() :The clear() method removes all items from the dictionary.

pop() :Removes and returns an element from a dictionary having the given key.

popitem():Removes the arbitrary key-value pair from the dictionary and returns it as tuple.

get() :It is a conventional method to access a value for a key.dictionary_name.values() returns a list of all the values available in a given dictionary.

str() :Produces a printable string representation of a dictionary.

update() :Adds dictionary dict2’s key-values pairs to dict

setdefault() :Set dict[key]=default if key is not already in dict

keys() :Returns list of dictionary dict’s keys

items() :Returns a list of dict’s (key, value) tuple pairs

has_key():Returns true if key in dictionary dict, false otherwise

fromkeys():Create a new dictionary with keys from seq and values set to value.

type() :Returns the type of the passed variable.

cmp() :Compares elements of both dict.

iterate through dictionary by :

Iterate through all keys

Iterate through all values

Iterate through all key, value pairs

1. Iterate through all keys :

statesAndCapitals = {

'Gujarat' : 'Gandhinagar',

'Maharashtra' : 'Mumbai',

'Rajasthan' : 'Jaipur',

'Bihar' : 'Patna'

}

for state in statesAndCapitals:

print(state)

2. Iterate through all values

for cap in statesAndCapitals.values():

print(cap)

3. # Iterating over values

for state, capital in statesAndCapitals.items():

print(state, ":", capital)