Is pop () in place python?

To get the result of removing (i.e, a new list, not in-place) a single item by index, there is no reason to use enumerate or a list comprehension or any other manual, explicit iteration.

Instead, simply slice the list before and after, and put those pieces together. Thus:

def skipping(a_list, index):
    return a_list[:index] + a_list[index+1:]

Let's test it:

>>> test = list('example')
>>> skipping(test, 0)
['x', 'a', 'm', 'p', 'l', 'e']
>>> skipping(test, 4)
['e', 'x', 'a', 'm', 'l', 'e']
>>> skipping(test, 6)
['e', 'x', 'a', 'm', 'p', 'l']
>>> skipping(test, 7)
['e', 'x', 'a', 'm', 'p', 'l', 'e']
>>> test
['e', 'x', 'a', 'm', 'p', 'l', 'e']

Notice that it does not complain about an out-of-bounds index, because slicing doesn't in general; this must be detected explicitly if you want an exception to be raised. If we want negative indices to work per Python's usual indexing rules, we also have to handle them specially, or at least -1 (it is left as an exercise to understand why).

Fixing those issues:

def skipping(a_list, index):
    count = len(a_list)
    if index < 0:
        index += count
    if not 0 <= index < count:
        raise ValueError
    return a_list[:index] + a_list[index+1:]

In this tutorial, we will learn about the Python List pop() method with the help of examples.

The pop() method removes the item at the given index from the list and returns the removed item.

Example

# create a list of prime numbers
prime_numbers = [2, 3, 5, 7]

# remove the element at index 2
removed_element = prime_numbers.pop(2)

print('Removed Element:', removed_element)
print('Updated List:', prime_numbers)

# Output: 
# Removed Element: 5
# Updated List: [2, 3, 7]

Syntax of List pop()

The syntax of the pop() method is:

list.pop(index)

pop() parameters

• The pop() method takes a single argument (index).
• The argument passed to the method is optional. If not passed, the default index -1 is passed as an argument (index of the last item).
• If the index passed to the method is not in range, it throws IndexError: pop index out of range exception.

Return Value from pop()

The pop() method returns the item present at the given index. This item is also removed from the list.

Example 1: Pop item at the given index from the list

# programming languages list
languages = ['Python', 'Java', 'C++', 'French', 'C']

# remove and return the 4th item
return_value = languages.pop(3)

print('Return Value:', return_value)
# Updated List
print('Updated List:', languages)

Output

Return Value: French
Updated List: ['Python', 'Java', 'C++', 'C']

Note: Index in Python starts from 0, not 1.

If you need to pop the 4th element, you need to pass 3 to the pop() method.

Example 2: pop() without an index, and for negative indices

# programming languages list
languages = ['Python', 'Java', 'C++', 'Ruby', 'C']

# remove and return the last item
print('When index is not passed:') 
print('Return Value:', languages.pop())

print('Updated List:', languages)

# remove and return the last item
print('\nWhen -1 is passed:') 
print('Return Value:', languages.pop(-1))

print('Updated List:', languages)

# remove and return the third last item
print('\nWhen -3 is passed:') 
print('Return Value:', languages.pop(-3))

print('Updated List:', languages)

Output

When index is not passed:
Return Value: C
Updated List: ['Python', 'Java', 'C++', 'Ruby']

When -1 is passed:
Return Value: Ruby
Updated List: ['Python', 'Java', 'C++']

When -3 is passed:
Return Value: Python
Updated List: ['Java', 'C++']

If you need to remove the given item from the list, you can use the remove() method.

And, you can use the del statement to remove an item or slices from the list.

Python list pop()is an inbuilt function in Python that removes and returns the last value from the List or the given index value.

Python List pop() Method Syntax

Syntax: list_name.pop(index)

• index (optional) – The value at index is popped out and removed. If the index is not given, then the last element is popped out and removed.

Return: ReturnsThe last value or the given index value from the list.

Exception: Raises IndexErrorWhen the index is out of range.

Python List pop() Method Example

Python3

l = [1, 2, 3, 4]

print("Popped element:", l.pop())

print("List after pop():", l)

Output:

Popped element: 4
List after pop(): [1, 2, 3]

Example 1: Using List pop() method to pop an element at the given index

Python3

list1 = [1, 2, 3, 4, 5, 6]

print(list1.pop(), list1)

print(list1.pop(0), list1)

Output:

6 [1, 2, 3, 4, 5]
1 [2, 3, 4, 5]

Example 2: DemonstratingIndexError 

Python3

list1 = [ 1, 2, 3, 4, 5, 6 ]

print(list1.pop(8))

Output: 

Traceback (most recent call last):
  File "/home/1875538d94d5aecde6edea47b57a2212.py", line 5, in 
    print(list1.pop(8))
IndexError: pop index out of range

Example 3: Practical Example

A list of the fruit contains fruit_name and property saying its fruit. Another list consume has two items juice and eat. With the help of pop() and append() we can do something interesting. 

Python3

fruit = [['Orange','Fruit'],['Banana','Fruit'], ['Mango', 'Fruit']]

consume = ['Juice', 'Eat']

possible = []

for item in fruit :

    for use in consume :

        item.append(use)

        possible.append(item[:])

        item.pop(-1)

print(possible)

Output: 

[['Orange', 'Fruit', 'Juice'], ['Orange', 'Fruit', 'Eat'],
 ['Banana', 'Fruit', 'Juice'], ['Banana', 'Fruit', 'Eat'],
 ['Mango', 'Fruit', 'Juice'], ['Mango', 'Fruit', 'Eat']]

Time Complexity : 

The complexity of all the above examples is constant O(1) in both average and amortized case 

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