Python Dictionary pop() Method

The Python pop() method removes and returns the value of a specified key from a dictionary. If the key isn't found, you can provide a default value to return instead of raising an error. Example:

d = {'a': 1, 'b': 2, 'c': 3}
v = d.pop('b')
print(v)  

v = d.pop('d', 'Not Found')
print(v) 

2
Not Found

Explanation:

• pop('b') removes key 'b' and returns 2, the dictionary becomes {'a': 1, 'c': 3}.
• pop('d', 'Not Found') returns 'Not Found' since 'd' doesn’t exist.

Syntax of Pop()

dict.pop(key, default)

Parameters:

• key: The key to be removed from the dictionary.
• default: (Optional) The value to return if the key isn't found. If not provided, a KeyError is raised if the key is missing.

Returns:

• If the key is found: It removes the key-value pair from the dictionary and returns the value associated with the key.
• If the key is not found: Returns the default value if provided, or raises a KeyError if no default value is provided.

Examples of pop()

Example 1: In this example, we remove the key from the dictionary using pop(). Since the key exists, it will be removed and its value will be returned.

d = {'name': 'Alice', 'age': 25}
val = d.pop('age')

print(val)      
print(d)

25
{'name': 'Alice'}

Explanation:

• pop('age') removes key 'age' and returns 25, the dictionary becomes {'name': 'Alice'} and print(d) shows the updated dictionary.

Example 2: In this example, we try to remove the key 'country' from the dictionary using pop(). Since the key does not exist and no default value is provided, Python will raise a KeyError.

d = {'city': 'Delhi'}
val = d.pop('country')

Output

Hangup (SIGHUP)
Traceback (most recent call last):
  File "/home/guest/sandbox/Solution.py", line 2, in <module>
    val = d.pop('country')
KeyError: 'country'

Explanation: pop('country') tries to remove key 'country', but it doesn't exist in the dictionary, so it raises a KeyError.

Example 3: In this example, we repeatedly remove the first key-value pair from the dictionary using pop(). We use a while loop that continues until the dictionary is empty.

d = {'a': 1, 'b': 2, 'c': 3}

while d:
    key = list(d.keys())[0]
    val = d.pop(key)
    print(f"Removed {key}: {val}")

Removed a: 1
Removed b: 2
Removed c: 3

Explanation: while loop repeatedly removes and prints the first key-value pair from the dictionary using pop() until the dictionary is empty.

Also Read:

• Python Dictionary Methods
• Python | Ways to remove a key from dictionary
• Python Dictionary popitem() method
• Python - Remove last element from dictionary

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