How to Create Dictionary in Python

Python comes with a variety of built-in data structures, capable of storing different types of data. A Python dictionary is one such data structure that can store data in the form of key-value pairs. The values in a Python dictionary can be accessed using the keys. In this article, we will be discussing the Python dictionary in detail.

Table of Contents

Creating a Dictionary

In Python, a Dictionary can be created by placing a sequence of elements within curly {} braces, separated by ‘comma’. Dictionary holds pairs of values, one being the Key and the other corresponding pair element being its Key:value. Values in a dictionary can be of any data type and can be duplicated, whereas keys can’t be repeated and must be immutable
 

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

Python3

# Creating a Dictionary# with Integer KeysDict = {1: 'Geeks', 2: 'For', 3: 'Geeks'}print("\nDictionary with the use of Integer Keys: ")print(Dict) # Creating a Dictionary# with Mixed keysDict = {'Name': 'Geeks', 1: [1, 2, 3, 4]}print("\nDictionary with the use of Mixed Keys: ")print(Dict)

Output: 

Dictionary with the use of Integer Keys: 
{1: 'Geeks', 2: 'For', 3: 'Geeks'}

Dictionary with the use of Mixed Keys: 
{1: [1, 2, 3, 4], 'Name': 'Geeks'}

Dictionary can also be created by the built-in function dict(). An empty dictionary can be created by just placing to curly braces{}. 

Python3

# Creating an empty DictionaryDict = {}print("Empty Dictionary: ")print(Dict) # Creating a Dictionary# with dict() methodDict = dict({1: 'Geeks', 2: 'For', 3:'Geeks'})print("\nDictionary with the use of dict(): ")print(Dict) # Creating a Dictionary# with each item as a PairDict = dict([(1, 'Geeks'), (2, 'For')])print("\nDictionary with each item as a pair: ")print(Dict)

Output: 

Empty Dictionary: 
{}

Dictionary with the use of dict(): 
{1: 'Geeks', 2: 'For', 3: 'Geeks'}

Dictionary with each item as a pair: 
{1: 'Geeks', 2: 'For'}

Nested Dictionary:

Python3

# Creating a Nested Dictionary# as shown in the below imageDict = {1: 'Geeks', 2: 'For',        3:{'A' : 'Welcome', 'B' : 'To', 'C' : 'Geeks'}} print(Dict)

Output: 

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

Adding elements to a Dictionary

In Python Dictionary, the Addition of elements can be done in multiple ways. One value at a time can be added to a Dictionary by defining value along with the key e.g. Dict[Key] = ‘Value’. Updating an existing value in a Dictionary can be done by using the built-in update() method. Nested key values can also be added to an existing Dictionary. 
 

Note- While adding a value, if the key-value already exists, the value gets updated otherwise a new Key with the value is added to the Dictionary.

Python3

# Creating an empty DictionaryDict = {}print("Empty Dictionary: ")print(Dict) # Adding elements one at a timeDict[0] = 'Geeks'Dict[2] = 'For'Dict[3] = 1print("\nDictionary after adding 3 elements: ")print(Dict) # Adding set of values# to a single KeyDict['Value_set'] = 2, 3, 4print("\nDictionary after adding 3 elements: ")print(Dict) # Updating existing Key's ValueDict[2] = 'Welcome'print("\nUpdated key value: ")print(Dict) # Adding Nested Key value to DictionaryDict[5] = {'Nested' :{'1' : 'Life', '2' : 'Geeks'}}print("\nAdding a Nested Key: ")print(Dict)

Output:  

Empty Dictionary: 
{}

Dictionary after adding 3 elements: 
{0: 'Geeks', 2: 'For', 3: 1}

Dictionary after adding 3 elements: 
{0: 'Geeks', 2: 'For', 3: 1, 'Value_set': (2, 3, 4)}

Updated key value: 
{0: 'Geeks', 2: 'Welcome', 3: 1, 'Value_set': (2, 3, 4)}

Adding a Nested Key: 
{0: 'Geeks', 2: 'Welcome', 3: 1, 5: {'Nested': {'1': 'Life', '2': 'Geeks'}}, 'Value_set': (2, 3, 4)}

Accessing elements from a Dictionary

In order to access the items of a dictionary refer to its key name. Key can be used inside square brackets. 

Python3

# Python program to demonstrate # accessing a element from a Dictionary # Creating a DictionaryDict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'} # accessing a element using keyprint("Accessing a element using key:")print(Dict['name']) # accessing a element using keyprint("Accessing a element using key:")print(Dict[1])

Output: 

Accessing a element using key:
For

Accessing a element using key:
Geeks

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

Python3

# Creating a DictionaryDict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'} # accessing a element using get()# methodprint("Accessing a element using get:")print(Dict.get(3))

Output: 

Accessing a element using get:
Geeks

Accessing an element of a nested dictionary

In order to access the value of any key in the nested dictionary, use indexing [] syntax.

Python3

# Creating a DictionaryDict = {'Dict1': {1: 'Geeks'},        'Dict2': {'Name': 'For'}} # Accessing element using keyprint(Dict['Dict1'])print(Dict['Dict1'][1])print(Dict['Dict2']['Name'])

Output: 

{1: 'Geeks'}
Geeks
For

Removing Elements from Dictionary

Using del keyword

In Python Dictionary, deletion of keys can be done by using the del keyword. Using the del keyword, specific values from a dictionary as well as the whole dictionary can be deleted. Items in a Nested dictionary can also be deleted by using the del keyword and providing a specific nested key and particular key to be deleted from that nested Dictionary.
 

Note: The del Dict will delete the entire dictionary and hence printing it after deletion will raise an Error.

Python3

# Initial DictionaryDict = { 5 : 'Welcome', 6 : 'To', 7 : 'Geeks',        'A' : {1 : 'Geeks', 2 : 'For', 3 : 'Geeks'},        'B' : {1 : 'Geeks', 2 : 'Life'}}print("Initial Dictionary: ")print(Dict) # Deleting a Key valuedel Dict[6]print("\nDeleting a specific key: ")print(Dict) # Deleting a Key from# Nested Dictionarydel Dict['A'][2]print("\nDeleting a key from Nested Dictionary: ")print(Dict)

Output: 

Initial Dictionary: 
{'A': {1: 'Geeks', 2: 'For', 3: 'Geeks'}, 'B': {1: 'Geeks', 2: 'Life'}, 5: 'Welcome', 6: 'To', 7: 'Geeks'}

Deleting a specific key: 
{'A': {1: 'Geeks', 2: 'For', 3: 'Geeks'}, 'B': {1: 'Geeks', 2: 'Life'}, 5: 'Welcome', 7: 'Geeks'}

Deleting a key from Nested Dictionary: 
{'A': {1: 'Geeks', 3: 'Geeks'}, 'B': {1: 'Geeks', 2: 'Life'}, 5: 'Welcome', 7: 'Geeks'}

Using pop() method

Pop() method is used to return and delete the value of the key specified.

Python3

# Creating a DictionaryDict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'} # Deleting a key# using pop() methodpop_ele = Dict.pop(1)print('\nDictionary after deletion: ' + str(Dict))print('Value associated to poped key is: ' + str(pop_ele))

Output: 

Dictionary after deletion: {3: 'Geeks', 'name': 'For'}
Value associated to poped key is: Geeks

Using popitem() method

The popitem() returns and removes an arbitrary element (key, value) pair from the dictionary.

Python3

# Creating DictionaryDict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'} # Deleting an arbitrary key# using popitem() functionpop_ele = Dict.popitem()print("\nDictionary after deletion: " + str(Dict))print("The arbitrary pair returned is: " + str(pop_ele))

Output: 

Dictionary after deletion: {3: 'Geeks', 'name': 'For'}
The arbitrary pair returned is: (1, 'Geeks')

 Using clear() method

All the items from a dictionary can be deleted at once by using clear() method.

Python3

# Creating a DictionaryDict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'}  # Deleting entire DictionaryDict.clear()print("\nDeleting Entire Dictionary: ")print(Dict)

Output: 

Deleting Entire Dictionary: 
{}

Dictionary Methods 

MethodsDescription
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.

Conclusion

Dictionary in Python is an unordered collection of data values, used to store data values like a map, which, unlike other Data Types that hold only a single value as an element, Dictionary holds key:value pair. Key-value is provided in the dictionary to make it more optimized.

0 0 votes
Article Rating
Subscribe
Notify of
guest
0 Comments
Inline Feedbacks
View all comments
0
Would love your thoughts, please comment.x
()
x