Filter index total from a list by passing the total value as a function argument-CodePudding

If I know perfectly how many indexes I'm looking for, I do it like this:

def main():
    lst = [['111','222','333'],['111','222','3333'],['111','222','333']]
    new_sublist = [[sublist[0],sublist[1]] for sublist in lst]
    print(new_sublist)

if __name__ == '__main__':
    main()

Result:

[['111', '222'], ['111', '222'], ['111', '222']]

Now I'm wanting to do the same thing but putting the amount of index as a function argument:

def main(total_index):
    lst = [['111','222','333'],['111','222','3333'],['111','222','333']]
 
    indexis = [f'sublist[{i}]' for i in range(total_index)]
    new_sublist = [eval(','.join(indexis)) for sublist in lst]
    print(new_sublist)

if __name__ == '__main__':
    main(2)

Result:

[('111', '222'), ('111', '222'), ('111', '222')]

But using loop and eval seems to me to be a very archaic way of dealing with this, is there a correct method to do this same work?

CodePudding user response：

You can just slice your list with [:len] notation

def main(total_index):
    lst = [['111','222','333'],['111','222','3333'],['111','222','333']]
    new_sublist = [sublist[:total_index] for sublist in lst]
    print(new_sublist)

if __name__ == '__main__':
    main(2)

CodePudding user response：

The slice method in @lejlot's answer is best, but if you want to see how to do it with a list comprehension without eval(), you can use a nested list comprehension:

def main(total_index):
    lst = [['111','222','333'],['111','222','3333'],['111','222','333']]
 
    new_sublist = [[sublist[i] for i in range(total_index)] for sublist in lst]
    print(new_sublist)