How to remove unwanted commas from a python list

Question

I'm doing an exercise from a python for beginners book. The project I'm stuck on is as follows: "Write a function that takes in a list of value as an argument and returns a string with all the items separated by comma and a space. Your function should be able to work with any list values passed to it"

Here is my code:

def passInList(spam):
       for x in range(len(spam)):
           z = spam[x] + ', ' 
           print(z,end= ' ')

spam=['apples', 'bananas', 'tofu', 'and cats']
passInList(spam)

Expected output is - 'apples, bananas, tofu, and cats'.

My output is- 'apples, bananas, tofu, and cats,'

The issue I'm having, is that I can't seems to get rid of the comma at the end of "cats".

Thanks for suggestions.

Not directly related to your problem, but: the assignment says you should return a string, but your function doesn't return anything. — Kevin, Aug 29 '16 at 20:13

score 2 · Answer 1 · answered Aug 29 '16 at 20:12

2

You could reduce your code to use join where you give it the separator and what list to join together.

def passInList(spam):
       print(', '.join(spam))

spam=['apples', 'bananas', 'tofu', 'and cats']
passInList(spam)

answered Aug 29 '16 at 20:12

depperm

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Thank you. (join worked) – AT_1965 Aug 29 '16 at 20:43

score 2 · Answer 2 · answered Aug 29 '16 at 20:32

As people have posted here, join already exists. But if the exercise is meant to understand how to implement join, then here is one possibility:

def passInList(spam):
    s = spam[0]
    for word in spam[1:]:
        s += ', ' + word
    return s

That is you take the first word, then you concatenate each of the next words using a comma.

Another option to implement this is using functional programming, namely, in this case, the reduce function:

def passInList(spam):
    return functools.reduce(lambda x, y: x + ', ' + y, spam)

Whenever a scheme of aggregating things, like in the previous implementation's s += ... is used, reduce comes to mind.

score 0 · Answer 3 · answered Aug 29 '16 at 20:12

0

Use join method:

spam=['apples', 'bananas', 'tofu', 'and cats']
print(', '.join(spam))

answered Aug 29 '16 at 20:12

Mateusz Moneta

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score 0 · Answer 4 · answered Aug 29 '16 at 20:12

0

add a if statement to only add a comma if x is smaller than len(spam) -1, or better yet, use the str class' join function

answered Aug 29 '16 at 20:12

Jules G.M.

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score 0 · Answer 5 · answered Aug 29 '16 at 20:31

You may use the join function which called with syntax 'str'.join(list). It joins all the elements in the list with str in between

>>> spam=['apples', 'bananas', 'tofu', 'and cats']
>>> my_string = ', '.join(spam)
>>> my_string
'apples, bananas, tofu, and cats'

How to remove unwanted commas from a python list

5 Answers5