CODEWITHSUNDEEP
pythonstringlistjoin
sam
sam

Reputation: 19164

Concatenate or print list elements with a trailing comma in Python

I am having a list as :

>>> l = ['1', '2', '3', '4']

if I use join statement,

>>> s = ', '.join(l)

will give me output as :

'1, 2, 3, 4'

But, what I have to do If I want output as :

'1, 2, 3, 4,'

(I know that I can use string concat but I want to know some better way)

.

Upvotes: 11

Views: 23301

Answers (8)

Christopher Stigson
Christopher Stigson

Reputation: 11

I don't know if this is what you are looking for? It works though.

l = [1,2,3,4]

for num in l: print(str(num), end=", ")

Upvotes: 0

jamylak
jamylak

Reputation: 133584

This IDLE session is a good example of how to pull the list elements into a string with a trailing comma:

>>> l = ['1', '2', '3', '4']
>>> ' '.join(x+',' for x in l)
'1, 2, 3, 4,'

Upvotes: 0

Tadeck
Tadeck

Reputation: 137390

String concatenation is the best way:

l = ['1', '2', '3', '4']  # original list
s = ', '.join(l) + ','

but you have other options also:

  1. Mapping to comma-ended strings, then joining:

    l = ['1', '2', '3', '4']  # original list
s = ' '.join(map(lambda x: '%s,' % x, l))

  2. Appending empty string to the joined list (don't modify original l list!):

    l = ['1', '2', '3', '4']  # original list
s = ', '.join(l + ['']).rstrip(' ')

  3. Using string formatting in place of concatenation:

    l = ['1', '2', '3', '4']  # original list
s = '%s,' % (', '.join(l))

Upvotes: 14

Zeugma
Zeugma

Reputation: 32105

If you are in Python 3, you could leverage the print built-in function:

print(*l, sep=', ', end=',')
  • *l unpacks the list of elements to pass them as individual arguments to print
  • sep is an optional argument that is set to in between elements printed from the elements, here I set it to ', ' with a space as you require
  • end is an optional argument that will be pushed at the and of the resulting printed string. I set it to ',' without space to match your need

You can use it starting Python 2.6 by importing the print function

from __future__ import print_function

However going this way has several caveats:

  • This is assuming you want to output the resulting string in stdout ; or you can redirect the output in a file with the file optional argument into a file
  • if you are in Python 2, the __future__ import can break you code compatibility so you would need to isolate your code in a separate module if the rest of your code is not compatible.

Long story short, either this method or the other proposed answers are a lot of efforts to try to avoid just adding a +',' at the end of the join resulting string

Upvotes: 7

okm
okm

Reputation: 23871

If you don't want concatenation, things could be hacky...

>>> l = [1, 2, 3, 4]
>>> repr(l+[0])[1:-3] # or str
'1, 2, 3, 4,'

Upvotes: 1

NPE
NPE

Reputation: 500495

Firstly, ','.join(l) won't work at all since it requires the elements to be strings, which they are not.

You can fix that and add the trailing comma like so:

In [4]: ', '.join(map(str, l)) + ','
Out[4]: '1, 2, 3, 4,'

I think this is by far the cleanest way to do it.

Upvotes: 1

Michael Wild
Michael Wild

Reputation: 26351

For str.join() to work, the elements contained in the iterable (i.e. a list here), must be strings themselves. If you want a trailing comma, just add an empty string to the end of your list.

Edit: To flesh it out a bit:

l = map(str, [1,2,3,4])
l.append('')
s = ','.join(l)

Upvotes: 5

unwind
unwind

Reputation: 399881

To include the spaces you've shown, you need to have a space in the separator string:

s = ", ".join(l) + ","

Or make it DRYer:

sep = ", "
s = (sep.join(l) + sep).rstrip()

In the latter, rstrip() is just used to remove the final trailing space (part of sep) since that's not in your desired output. It's not the cheapest way of doing this, but it's pretty clear.

Upvotes: 1

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