python - why map(outer.remove, inner) does not work to remove inner from outer

Please help understand why applying the outer.remove method on inner doe not remove the inner list elements from the outer list.

My sincere apology for having asked python - List.remove method not applicable as the function with the map builtin? wrongly, hence opening a new question.

I thought List.remove would be a function associated to the outer list object, hence applying it to inner would update the outer list via map. However, apparently the <built-in method remove of list object at 0x7fbd8411a840> is not updating the outer list it is associated to.

Please help understand if this is work as designed and what is happening under the hood in the Python interpreter. If there is a way to apply <list object>.remove via the map builtin.

import copy    n = 10  outer = list(range(1, 2*n+1))  inner = list(range(1, n+1))    print(f"outer is {outer}")  print(f"inner is {inner}\n")    _outer = copy.deepcopy(outer)  for i in inner:      _outer.remove(i)  print(f"for loop application of outer.remove(inner_element) is \n{_outer}\n")    print(f"outer.remove is {outer.remove}")  map(outer.remove, inner)  print(f"map application of outer.remove is \n{outer}")  

Result

outer is [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]  inner is [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]    for loop application of outer.remove(inner_element) is   [11, 12, 13, 14, 15, 16, 17, 18, 19, 20]    outer.remove is <built-in method remove of list object at 0x7fbd8411a840>  map application of outer.remove is   [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]  

https://stackoverflow.com/questions/65894558/python-why-mapouter-remove-inner-does-not-work-to-remove-inner-from-outer January 26, 2021 at 09:07AM