CODEWITHSUNDEEP
python
Lss
Lss

Reputation: 75

How do I add an element to each list in a list of lists?

I'm stuck at a problem where I need a function that takes two arguments, one character and a lists that contains list. The function is then supposed to add that element to all the lists in the list. So if I have the arguments "o" and [['tesc'], ['fo'], [1]] the output should be [['tesc', 'o'], ['fo', 'o'], [1, 'o']]

Here's my code, I suspect that I'm not doing anything right as I don't get any output at all

def distribute(e, l):
    new_list = []
    for i in l:
        new_list.append(i)
    for e in new_list:
        new_list.append(e)
    print(new_list)

What am I doing wrong?

Upvotes: 0

Views: 657

Answers (3)

Joe Iddon
Joe Iddon

Reputation: 20414

You are using the same variable name 'e' in the for-loop and as a function parameter. Also, in this second loop, you want to append to i as these are the sub lists - not append to new_list.

This is why the function never completes as you are looping through each element in new_list but adding to new_list as you do so so it never ends.

Finally, I would change the print to return as you are writing a function:

def distribute(e, l):
    new_list = []
    for i in l:
        new_list.append(i)
    for i in new_list:
        i.append(e)
    return new_list

This will work, however it is not very pythonic. All the first for-loop is doing is creating a copy of the input list ('l') which is necessary (in some applications) as without it, the input list would be modified as lists are immutable.

However, you could get rid of this loop altogether by just copying the list with a slice. This would make your function more succinct:

def distribute(e, l):
    new_list = l[:]
    for i in new_list:
        i.append(e)
    return new_list

And of course, if you do not care if the list parsed into the function is modified, you can not bother making a copy of it:

def distribute(e, l):
    for i in l:
        i.append(e)
    return l

Upvotes: 1

martineau
martineau

Reputation: 123463

You're making things too complicated:

def distribute(e, l):
    for sublist in l:
        sublist.append(e)

    print(l)

distribute("o", [['tesc'], ['fo'], [1]])

Output:

[['tesc', 'o'], ['fo', 'o'], [1, 'o']]

Upvotes: 1

Ajax1234
Ajax1234

Reputation: 71451

You can try this:

def add_item(l, a):
   return [i+[a] for i in l]

print(add_item([['tesc'], ['fo'], [1]], "o"))

Output:

[['tesc', 'o'], ['fo', 'o'], [1, 'o']]

Upvotes: 1

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