Python - Dictionary Methods

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In this tutorial we will learn about dictionary methods in Python.

In the previous tutorial Python - Dictionary we learned about dictionary. Feel free to check that out.

Quick recap

  • A dictionary is an unordered collection of key-value pairs.
  • We use curly { } brackets to create dictionary.
  • The key is separated from the value using : colon.
  • Each key-value pair of the dictionary is separated by , comma.

Alright, let's get started with dictionary methods.

clear

We use the clear method to remove all the items from the dictionary.

In the following Python program we are removing all the items from the given dictionary.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

user.clear()

copy

We use the copy method to make a copy of an existing dictionary.

In the following Python program we are creating a copy of a given dictionary.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

x = user.copy()

fromkeys

We use the fromkeys method to create a dictionary with given keys and values.

In the following Python program we are creating a dictionary using keys passed to the fromkeys method.

# keys
keys = ("a", "b", "c")

myDict = dict.fromkeys(keys)

print(myDict)

We will get the following output.

{'a': None, 'b': None, 'c': None}

Note! If the value is not passed then None is used as the default value.

In the following Python program we are creating a dictionary using the keys passed to the fromkeys method and we are setting all the keys to 0.

# keys and value
keys = ("a", "b", "c")
value = 0

myDict = dict.fromkeys(keys, value)

print(myDict)     # {'a': 0, 'b': 0, 'c': 0}

get

We use the get method to get value of a specific key of a given dictionary.

In the following Python program we are getting the value of the "score" key.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

print(user.get('score'))    # 9.1

Note! If the key does not exists in the given dictionary then we will get None.

items

We use the items method to get a list that consists of tuples made up of key-value pairs of a given dictionary.

In the following Python program we are creating a dictionary list using the items method.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

items = user.items()

print(items)

We will get the following output.

dict_items([('username', 'yusufshakeel'), ('score', 9.1), ('isOnline', False)])

keys

We use the keys method to get all the keys of a given dictionary.

In the following Python program we are getting the keys.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

keys = user.keys()

print(keys)

We will get the following output.

dict_keys(['username', 'score', 'isOnline'])

pop

We use the pop method to remove a specific item (key-value pair) from the dictionary using a given key.

In the following Python program we are removing the "isGameOver" item from the dictionary using the pop method.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False,
    "isGameOver": False
}

item = user.pop('isGameOver')

print(item)    # False
print(user)    # {'username': 'yusufshakeel', 'score': 9.1, 'isOnline': False}

popitem

We use the popitem to remove the last inserted item from the dictionary.

In the following Python program we are inserting a new item and then popping it.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

# insert item
user['isGameOver'] = False

print("before:", user)

# pop item
item = user.popitem()

print("popitem:", item)

print("after:", user)

Output

before: {'username': 'yusufshakeel', 'score': 9.1, 'isOnline': False, 'isGameOver': False}
popitem: ('isGameOver', False)
after: {'username': 'yusufshakeel', 'score': 9.1, 'isOnline': False}

setdefault

We use the setdefault method to get the value of a specified key.

If the key does not exists in the dictionary then the key is inserted with the given value passed to the setdefault method.

In the following Python program we will get back the value of "score" key as it exists in the dictionary.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

item = user.setdefault('score', 9.2)

print(item)
print(user)

Output:

9.1
{'username': 'yusufshakeel', 'score': 9.1, 'isOnline': False}

In the following Python program the key "isGameOver" is added to the dictionary as it does not exists.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

item = user.setdefault('isGameOver', False)

print(item)
print(user)

Output

False
{'username': 'yusufshakeel', 'score': 9.1, 'isOnline': False, 'isGameOver': False}

update

We use the update method to insert an item in the dictionary.

In the following Python program we are inserting a new item (key-value pair) isGameOver: False in the given dictionary.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

user.update({'isGameOver': False})

print(user)

Output:

{'username': 'yusufshakeel', 'score': 9.1, 'isOnline': False, 'isGameOver': False}

values

We use the values method to get all the values of a dictionary.

In the following Python program we are printing all the values of a given dictionary.

# dict
user = {
    "username": "yusufshakeel",
    "score": 9.1,
    "isOnline": False
}

values = user.values()

print(values)

We will get the following output.

dict_values(['yusufshakeel', 9.1, False])
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