how to remove an element from a nested list?

Question

if i have an nested list such as:

m=[[34,345,232],[23,343,342]]

if i write m.remove(345) it gives an error message saying elem

Answer 1

You can delete by using delete:- del m[1][1] or by using below code

for i in m:
    for j in i:
        if j==345:
            i.remove(j)
print(m)

Answer 2

A shortcut of doing this is using del command:

del list[element] element[nested element] 

del [] []

Answer 3

There is no shortcut for this. You have to remove the value from every nested list in the container list:

for L in m:
    try:
        L.remove(345)
    except ValueError:
        pass

If you want similiar behavior like list.remove, use something like the following:

def remove_nested(L, x):
    for S in L:
        try:
            S.remove(x)
        except ValueError:
            pass
        else:
            break  # Value was found and removed
    else:
        raise ValueError("remove_nested(L, x): x not in nested list")

Answer 4

You can remove 345 by using this code.

m[0].remove(345)

Answer 5

If you have more than one nested level this could help

def nested_remove(L, x):
    if x in L:
        L.remove(x)
    else:
        for element in L:
            if type(element) is list:
                nested_remove(element, x)

>>> m=[[34,345,232],[23,343,342]]
>>> nested_remove(m, 345)
>>> m
[[34, 232], [23, 343, 342]]

>>> m=[[34,[345,56,78],232],[23,343,342]]
>>> nested_remove(m, 345)
>>> m
[[34, [56, 78], 232], [23, 343, 342]]

Answer 6

If you want to remove only by indexes you can use this method

m[0].pop(1)

by this you can specify only the index. This is helpful if you know only the position you want to remove.