How to remove item equal to some value from list of lists?

Question

I need to remove all item[0] if a is == '1':

a = [['1','2','3'], ['2','4','9']]
for item in a:
    if item[0] == '1':
        del item

This is not the correct way to ask questions , mind the typos, give some details instead of just posting some random thoughts in order to get proper help — Doodle, Mar 21 '18 at 15:10

score 3 · Answer 1 · answered Mar 21 '18 at 15:08

3

You can use a list comprehension as follows

a = [i for i in a if i[0] != '1']

answered Mar 21 '18 at 15:08

Cory Kramer

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score 1 · Answer 2 · answered Mar 21 '18 at 15:12

1

Do not change length of list while iterating over it. make new list instead.

b = [i for i in a if i[0] != '1']

answered Mar 21 '18 at 15:12

Rahul

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score 0 · Answer 3 · answered Mar 21 '18 at 15:08

0

Use filter:

new_a = list(filter(lambda item: item[0] != '1', a))

The list is just so its compatible regardless of your python version (filter returns lazy sequence in python3).

answered Mar 21 '18 at 15:08

Reut Sharabani

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score 0 · Answer 4 · answered Mar 22 '18 at 22:28

A List Comprehension is the best way to solve this problem but if you want to use a for loop here's some Python code for that:

a = [[1,2,3], [2,1,9], [1,6,9], [5,6,7]]
# Code
def removeOneList(a):

    for item in a:
       if item[0] == 1:
           del item[:]

    return a

print(removeOneList(a))

How to remove item equal to some value from list of lists?

4 Answers4