CODEWITHSUNDEEP
pythonpython-3.xlist
user9940344
user9940344

Reputation: 584

How to remove an element from all lists in a list of lists?

Suppose I have a list of lists.

L = [[1,2,3], ['a',2,True],[1,44,33,12.1,90,2]]

I want to be able to remove all instances of a specific element from each of the sublists in the list L.

So for instance I might want to remove the number 2 so this would produce

L = [[1,3], ['a',True],[1,44,33,12.1,90]]

I tried to use this function + code:

def remove_values_from_list(the_list, val):
    return [value for value in the_list if value != val]

for i in L:
    i = remove_values_from_list(i, '2')

However the output still gives L in its original form and doesn't remove the 2.

Upvotes: 0

Views: 195

Answers (2)

Amadan
Amadan

Reputation: 198324

i is a variable that is not connected to L. It is assigned a value from L, then you reassign it to something else; this will not affect L at all.

A non-destructive way to do this (i.e. preserve L, make a new list for the result):

newL = [[value for value in the_list if value != val] for the_list in L]

A destructive way (i.e. change L itself):

for the_list in L:
    while value in the_list:
        the_list.remove(value)

Upvotes: 5

Arkistarvh Kltzuonstev
Arkistarvh Kltzuonstev

Reputation: 6920

Try this :

def remove_values_from_list(the_list, val):
    return [[v for v in l1 if v!= val] for l1 in the_list]

In your code, you were checking whether only one sub-list is equivalent to the the val parameter. You need to check it inside sub-lists. Also a secondary mistake would be to check items inside sub-lists with exact type. You are searching for '2' (str type) where as there is 2 (int type) in the sub-lists.

Upvotes: 0

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