A Dictionary is a built-in data type used in Python in order to store data in the form of ‘key: value’ pairs. Dictionaries are unordered (starting from Python 3.7, they preserve insertion order), mutable, and indexed collections where each key is unique and maps to a value. It is generally used to store related data, such as information associated with a specific entity or object, where the value can be retrieved easily based on the key.
The Dictionary methods in Python are known as a collection of various functions that operate on a dictionary.
Python Dictionary Methods
There are several Python Dictionary Methods that enable us to perform multiple tasks, such as manipulation, access, and transformation, with efficiency and precision.
| Function | Explanation |
|---|---|
| fromkeys() | This method returns the dictionary with the key mapped to the value given in the “value” parameter. |
| pop() | This method is used to remove an element from the dictionary |
| clear() | This method is used to clear or delete all the elements from the dictionary. |
| popitem() | This method returns and removes the element that was added to the dictionary last. It is like last in, first out (LIFO). |
| copy() | This method returns a shallow copy of the dictionary. |
| get() | This method returns the value for the given key. |
| setdefault() | This method returns a value with a specified key. If there is no key, it will insert a key with the specified value. |
| items() | This returns all dictionary that has a value assigned. |
| keys() | This method returns a list of keys of the dictionary. |
| update() | This method is used to update the dictionary. |
| values() | This method returns a list of the dictionary values. |
Python Built-in Dictionary Methods
1. Dictionary fromkeys() Method
The dictionary fromkeys() method in Python returns the dictionary with the key mapped to the value given in the ‘value’ parameter. It does not change anything in the given dictionary; instead, it creates a new dictionary in the sequence of the specified values.
Syntax:
The syntax of the fromkeys() method is shown below:
dict.fromkeys(keys, value) Parameters:
- keys: This parameter represents the keys to be transformed into a dictionary.
- value: It is optional. It represents the value for all your keys. The default value is set to None.
Note: The value that you specify in the value parameter is assigned to all the keys of the dictionary.
Returns: This method returns a dictionary with keys. If the keys are mapped to none, it returns no value; otherwise, it returns the respective value provided for that field.
Example: Dictionary fromkeys() Method
Let us see an example to understand the working of the fromkeys() method in Python.
Example
# given set of keys
keys = {'a', 'e', 'i', 'o', 'u'}
# creating a dictionary using fromkeys()
dict_1 = dict.fromkeys(keys) # not specified any value
print("Dictionary 1 (without values):", dict_1) # set default values to none
# initializing a variable to store a value
value = 'vowel'
dict_2 = dict.fromkeys(keys, value) # specifying a default value
print("Dictionary 2 (with default value):", dict_2)Output:
Dictionary 1 (without values): {'o': None, 'i': None, 'a': None, 'e': None, 'u': None}
Dictionary 2 (with default value): {'o': 'vowel', 'i': 'vowel', 'a': 'vowel', 'e': 'vowel', 'u': 'vowel'}
2. Dictionary pop() Method
In Python, the dictionary pop() method is used to remove an element from the dictionary. This method removes the element from the specified key in the given list.
If the particular key is present in the dictionary, it is removed from the dictionary, and the value is returned. If the specified key is not present, it raises a KeyError error.
Syntax:
The syntax of the pop() method is shown below:
dictionary_name.pop(key, default_value)
Parameters:
- key:A key to delete the value associated with it.
- default_value:If the key is not present, the default value is returned.
Return: It removes and returns the value associated with the specified key.
Example: Dictionary pop() Method
Let us see an example to understand the working of the pop() method in Python.
Example
# simple example of Python dictionary pop() method
# given dictionary
fruits = {
'apple': 20,
'banana': 14,
'watermelon': 2,
'kiwi': 12,
'oranges': 24
}
print("Given Dictionary:", fruits)
# using the pop() method to remove the specified key
popped_value = fruits.pop('kiwi')
print("Popped Value:", popped_value)
print("Updated Dictionary:", fruits)Output:
Given Dictionary: {'apple': 20, 'banana': 14, 'watermelon': 2, 'kiwi': 12, 'oranges': 24}
Popped Value: 12
Updated Dictionary: {'apple': 20, 'banana': 14, 'watermelon': 2, 'oranges': 24}
Explanation
In the above example, we are given a dictionary. We used the pop() method to remove the specified key from the dictionary. As a result, the key is removed, and the value associated with that key is returned.
3. Dictionary clear() Method
The Dictionary clear() method in Python is used to clear, delete, or remove all the elements from the dictionary. It removes everything in key-value pairs and makes the dictionary empty.
Syntax:
The syntax of the clear() method is shown below:
NameoftheDictionary.clear()
Parameters: This method does not accept any parameters.
Return Value: This method does not return any value.
Example: Dictionary clear() Method
Let us see an example to understand the working of the clear() method in Python.
Example
new_dictionary = {'1': 'Welcome', '2': 'to', '3': 'Lean Python App'}
new_dictionary.clear()
print("Printing the dictionary after .clear() method: \n", new_dictionary)Output:
Printing the dictionary after .clear() method:
{}
Explanation
In the above example, we are given a dictionary. We used the clear() method to remove all the elements from the dictionary. As a result, all the elements are removed, and an empty dictionary is returned.
4. Dictionary popitem() Method
The popitem() method in Python is used to remove the item (key and value pair) that was last added to the dictionary. keyError is raised, just in case the dictionary is empty.
Syntax:
The syntax of the popitem() method is shown below:
NameoftheDictionary.popitem()Parameters: This method does not accept any parameters.
Return Value: This method returns a new dictionary after removing the last added item in the dictionary.
Example: Dictionary popitem() Method
Let us see an example to understand the working of the popitem() method in Python.
Example
dictionary_data = {'Welcome': 1, 'to': 2, 'Learn Python App': 3}
item = dictionary_data.popitem()
print("The item is:",item)
print("The dictionary obtained is:",dictionary_data)Output:
The item is: ('Learn Python App', 3)
The dictionary obtained is: {'Welcome': 1, 'to': 2}
Explanation
In the above example, we are given a dictionary. We used the popitem() method to remove the last added item from the dictionary. As a result, a new dictionary is returned after removing the last added item.
5. Dictionary copy() Method
The copy() method in Python is used to create and return a shallow copy of the dictionary.
A shallow copy creates a new object that looks exactly like the original object-s structure, apart from its nested contents. The top-level properties are copied into a new dictionary, while any referenced objects inside it still point to the same memory locations as those in the original. In conclusion, only the container is duplicated while the overall reference values remain the same.
Syntax:
The syntax of the copy() method is shown below:
NameoftheDictionary.copy()
Parameters: This method does not accept any parameters.
Return Value: This method returns a shallow copy of the present dictionary.
Example: Dictionary copy() Method
Let us see an example to understand the working of the copy() method in Python.
Example
first_dictionary = {'Name': 'Learn Python App', 'Topic': 'Python Copy Method'};
second_dictionary = first_dictionary.copy()
print ("New Dictionary : %s" % str(second_dictionary))Output:
New Dictionary : {'Name': 'Learn Python App', 'Topic': 'Python Copy Method'}Explanation
In the above example, we are given a dictionary named first_dictionary. Then created a shallow copy of this dictionary in the new dictionary named second_dictionary and printed the output.
Example: Updating the elements of a Dictionary
Let us see an example of updating the elements of a dictionary using the copy() method:
Example
- first_dictionary = {1: ‘Learn Python App’, 2: ‘Python Dictionary Methods’, 3: [2, 0, 5]}
- print(“The given dictionary is: “, first_dictionary)
- # using copy() method to copy
- new_dictionary = first_dictionary.copy()
- print(“The new copied dictionary is: “, new_dictionary)
- # Updating the elements in the second dictionary
- new_dictionary[1] = ‘Python Copy Method’
- # updating the items in the list
- new_dictionary[3][2] = 404
- print(“The updated dictionary is: “, new_dictionary)
Output:
The given dictionary is: {1: 'Learn Python App', 2: 'Python Dictionary Methods', 3: [2, 0, 5]}
The new copied dictionary is: {1: 'Learn Python App', 2: 'Python Dictionary Methods', 3: [2, 0, 5]}
The updated dictionary is: {1: 'Python Copy Method', 2: 'Python Dictionary Methods', 3: [2, 0, 404]}
Explanation
In the above example, we are given a dictionary named first_dictionary. We copied the elements of this dictionary into a second but new dictionary named new_dictionary and then printed it.
After this, we updated to elements of the new_dictionary and printed the output.
6. Dictionary get() Method
The get() method in Python is used to get the value of the key specified by the user. If the key is not present in the dictionary, it will return None.
Syntax:
The syntax of the get() method is shown below:
NameoftheDictionary.get(key, value)Parameters:
- key: The key is specified by the user, and it-s to be searched in the dictionary
- value: The value assigned to the specified key is returned. If the key does not exist, it will return None.
Example: Dictionary get() Method
Let us see an example to understand the working of the get() method in Python.
Example
car_details = {
"brand": "Tata",
"model": "Sierra",
"year": 2025
}
a = car_details.get("model")
print(a)Output:
SierraExplanation
In the above example, we have a dictionary named car_details consisting of details of cars. We used the get() method to extract the -model- key from the dictionary.
Example: When the Key does not exist
Let us see an example to see what happens when the key does not exist while using the get() method:
Example
car_details = {
"brand": "Tata",
"model": "Sierra",
"year": 2025
}
a = car_details.get("kilometres_driven")
print(a)Output:
NoneExplanation
In the above example, we have a dictionary named car_details in which we have the details of a car, such as brand, model, and year.
By using the get() method, we try to extract the value of the key “kilometres_driven,” but as this key does not exist in the dictionary, the get() function returns None instead of raising an error. At last, none was returned as the output.
7. Dictionary setdefault() Method
The setdefault() method in Python is used to return a value with a specified key. If there is no key, it will insert a key with the specified value. None is the default value of the key.
Syntax:
The syntax of the setdefault() method is shown below:
NameoftheDictionary.setdefault(key, default=None)Parameters
- key: The key is specified by the user, and it-s to be searched in the dictionary
- value: If the key is not found, this value is destined to be returned. The default value is None.
Example: Dictionary setdefault() method
Let us see an example to understand the working of the setdefault() method in Python.
Example
#Creating a dictionary
dictionary = {'Car Brand': 'Tata', 'Model': 'Sierra'}
# printing the first result
print ("Value : %s" % dictionary.setdefault('Model'))Output:
Value : SierraExplanation
In the above example, we have a dictionary consisting of Car Brand and Model keys with their values, Tata and Sierra, respectively. Then we printed the Model key from the dictionary, and it returned -Sierra- as the output.
Example: None Default Value
Let us see an example to understand the significance of the None default value.
Example
#Creating a dictionary
dictionary = {'Car Brand': 'Tata', 'Model': 'Sierra'}
#key doesn't exist
print ("Value : %s" % dictionary.setdefault('Age'))Output:
Value : NoneExplanation
In the above example, we have a dictionary consisting of Car Brand and Model keys with their values, Tata and Sierra, respectively. Then we tried to print the value of key -Age-, but since it does not exist, the default key, which is None, is returned.
8. Dictionary items() Method
The items() method in Python is used to return all the items of the dictionary that have a value assigned.
When we update the dictionary, the items that are returned also get changed. As we know, that dictionary Dictionaries are unordered (starting from Python 3.7, they preserve insertion order), mutable, and indexed collections where each key is unique and maps to a value. It is generally used to store related data, such as information associated with a specific entity or object, where the value can be retrieved easily based on the key.
Syntax:
The syntax of the items() method is shown below:
The following is the syntax of the items() method:
NameoftheDictionary.items()Parameters: This method does not accept any parameters.
Return Value: The item() returns the output in the form of a list with key-value pairs in a tuple.
Example: Dictionary items() method
Let us see an example to understand the working of the items() method in Python.
Example
dictionary = {'A': 'Learn Python App', 'B': 'Python', 'C': 'Dictionary', 'D': 'Methods'}
# using items() to get all key-value pairs
items = dictionary.items()
print(items)Output:
dict_items([('A', 'Learn Python App'), ('B', 'Python'), ('C', 'Dictionary'), ('D', 'Methods')])
Explanation
In the above example, we have created a dictionary and printed all items present in key-value pairs in a tuple, which is present inside a dictionary.
Example: Updating the Dictionary
Let us see an example of updating the dictionary using the items() method in Python
Example
dictionary = {'A': 'Learn Python App', 'B': 'Python', 'C': 'Dictionary', 'D': 'Methods'}
# using items() to get all key-value pairs
items = dictionary.items()
print(items)
#updating the dictionary
dictionary['A'] = 'Welcome to Learn Python App'
print("Dictionary after updating: ", items)Output:
dict_items([('A', 'Learn Python App'), ('B', 'Python'), ('C', 'Dictionary'), ('D', 'Methods')])
Dictionary after updating: dict_items([('A', 'Welcome to Learn Python App'), ('B', 'Python'), ('C', 'Dictionary'), ('D', 'Methods')])
Explanation
In the above example, we have created a dictionary and printed all items present in key-value pairs in a tuple, which is present inside a dictionary. Then we updated the value of the ‘A’ key from ‘Tpoint Tech’ to ‘Welcome to TpointTech’ and printed the updated dictionary.
9. Dictionary keys() Method
The method is used to extract and return the list of keys of the dictionary.
Syntax:
The syntax of the keys() method is shown below:
NameoftheDictionary.keys()Parameters: This method does not accept any parameters.
Return Value: The item() method returns the return the list of keys of the dictionary.
Example: keys() method
Let us see an example to understand the working of the keys() method in Python.
Example
#Creating a dictionary
car_details = {'Car Brand': 'Tata', 'Model': 'Sierra', 'Year': 2025}
# extracts and prints the keys of the dictionary
keysmethod= car_details.keys()
print(keysmethod)Output:
dict_keys(['Car Brand', 'Model', 'Year'])Explanation
In the above example, we have a dictionary car_details with the keys and values. We use the keys() method to extract and print the keys only, which are ‘Car Brand’, ‘Model’, and ‘Year’.
Example: Updating the Dictionary
Let us see an example of updating the dictionary using the keys() method in Python.
Example
#Creating a dictionary
car_details = {'Car Brand': 'Tata', 'Model': 'Sierra', 'Year': 2025}
# extracts and prints the keys of the dictionary
keysmethod= car_details.keys()
print('Before the update of dictionary:', keysmethod)
#updating the dictionary
# adding an element to the dictionary
car_details.update({'price': '11.99 Lakhs only'})
# prints the updated dictionary
print('Dictionary after the update:', keysmethod)Output:
Before the update of the dictionary: dict_keys(['Car Brand', 'Model', 'Year'])
Dictionary after the update: dict_keys(['Car Brand', 'Model', 'Year', 'price'])
Explanation
In the above example, we have a dictionary car_details with the keys and values. We use the keys() method to extract and print the keys only, which are ‘Car Brand’, ‘Model’, and ‘Year’. Then we added an element and printed the keys of the updated dictionary, which consisted of the addition of -price-.
10. Dictionary values() Method
The values() method allows us to return a view object consisting of all values from the dictionary, which can be accessed and iterated efficiently.
Syntax:
The syntax of the values() method is shown below:
NameoftheDictionary.values()Parameters: This method does not accept any parameters.
Return Value: The values() method returns a list of the dictionary values.
Example: Dictionary values() Method
Let us take a look at an example showing how to use the values() method in Python.
Example
#Creating a dictionary
car_details = {'Car Brand': 'Tata', 'Model': 'Sierra', 'Year': 2025}
# extracts and prints the values of the dictionary
valuesmethod= car_details.values()
print(valuesmethod)Output:
dict_values(['Tata', 'Sierra', 2025])Explanation
In the above example, we have a dictionary car_details with the keys and values. We use the values() method to extract and print the values only, which are ‘Tata’, ‘Sierra’, and 2025.
Example: Updating the Dictionary
Let us take a look at an example of updating the dictionary using the values() method in Python.
Example
#Creating a dictionary
car_details = {'Car Brand': 'Tata', 'Model': 'Sierra', 'Year': 2025}
# extracts and prints the values of the dictionary
valuesmethod= car_details.values()
print("The values of the dictionary before appending are: ", valuesmethod)
# Appending an item to the dictionary
car_details['Fuel Type'] = 'Petrol'
# Printing the result
print ("The values of the dictionary after appending are: ", valuesmethod)Output:
The values of the dictionary before appending are: dict_values(['Tata', 'Sierra', 2025])
The values of the dictionary after appending are: dict_values(['Tata', 'Sierra', 2025, 'Petrol'])
Explanation
In the above example, we have a dictionary car_details with the keys and values. We use the values() method to extract and print the values of the dictionary before updating, which are ‘Tata’, ‘Sierra’, and 2025.
After that, we append an item in the dictionary, where we created a new key named -Fuel_Type,- and its value is Petrol. Then, we printed the values, and the output was: ([‘Tata’, ‘Sierra’, 2025, ‘Petrol’]).
11. Dictionary update() Method
The update() method is used to update the items in the dictionary or an iterable object with key-value pairs.
Syntax:
The syntax of the update() method is shown below:
NameoftheDictionary.update([other])Parameters: This method accepts the elements that must be replaced with a dictionary or an iterable pair of key/value.
Return Value: The values() return the dictionary or iterable pairs of keys and values with updated elements.
Example: Dictionary update() Method
Let us see a simple example showing the use of the update() method in Python.
Example
# using the update() method in Dictionary
# Dictionary with three items
first_dictionary = {'A': 'LearnPython', 'B': 'Python', }
second_dictionary = {'B': 'Dictionary', 'C': 'Methods'}
# updating first dictionary
first_dictionary.update(A='Welcome to LearnPython')
print(first_dictionary)
#updating second dictionary
second_dictionary.update(B='We are learning Dictionary')
print(second_dictionary)Output:
{'A': 'Welcome to LearnPython', 'B': 'Python'}
{'B': 'We are learning Dictionary', 'C': 'Methods'}
Explanation
In the above example, we have two dictionaries, first_dictionary and second_dictionary. The update() method was used to update the values of key A to -Welcome to Tpoint Tech- from -Tpoint Tech- and key B to -We are learning Dictionary- from -Dictionary- in both dictionaries, respectively.
Example: Updating the dictionary with Keyword Arguments
Let us take a look at an example of updating the dictionary with keyword arguments in Python.
Example
#updating the dictionary with only keyword arguments
# Here we have only one dictionary
dictionary = {'A': 'Lean'}
# Update the Dictionary with an iterable
dictionary.update(B='Python', C='App')
print(dictionary)Output:
'A': 'Learn', 'B': 'Python', 'C': 'App'}
