sachin irukula sachin irukula - 3 months ago 28
Python Question

Difference between del, remove and pop on lists

>>> a=[1,2,3]
>>> a.remove(2)
>>> a
[1, 3]
>>> a=[1,2,3]
>>> del a[1]
>>> a
[1, 3]
>>> a= [1,2,3]
>>> a.pop(1)
2
>>> a
[1, 3]
>>>


Is there any difference between the above three methods to remove an element from a list?

Answer

Yes, remove removes the first matching value, not a specific index:

>>> a = [0, 2, 2, 3]
>>> a.remove(2)
>>> a
[0, 2, 3]

del removes a specific index:

>>> a = [3, 2, 2, 1]
>>> del a[1]
[3, 2, 1]

and pop returns the removed element:

>>> a = [4, 3, 5]
>>> a.pop(1)
3
>>> a
[4, 5]

Their error modes are different too:

>>> a = [4, 5, 6]
>>> a.remove(7)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: list.remove(x): x not in list
>>> del a[7]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list assignment index out of range
>>> a.pop(7)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: pop index out of range