Python, print delimited list

>>> ','.join(map(str,a))
'1,2,3'

A ','.join as suggested in other answers is the typical Python solution; the normal approach, which peculiarly I don't see in any of the answers so far, is

print ','.join(str(x) for x in a)

known as a generator expression or genexp.

If you prefer a loop (or need one for other purposes, if you're doing more than just printing on each item, for example), there are of course also excellent alternatives:

for i, x in enumerate(a):
  if i: print ',' + str(x),
  else: print str(x),

this is a first-time switch (works for any iterable a, whether a list or otherwise) so it places the comma before each item but the first. A last-time switch is slightly less elegant and it work only for iterables which have a len() (not for completely general ones):

for i, x in enumerate(a):
  if i == len(a) - 1: print str(x)
  else: print str(x) + ',',

this example also takes advantage of the last-time switch to terminate the line when it's printing the very last item.

The enumerate built-in function is very often useful, and well worth keeping in mind!

There are two options ,

You can directly print the answer using print(*a, sep=',') this will use separator as "," you will get the answer as ,

1,2,3

and another option is ,

print(','.join(str(x) for x in list(a)))

this will iterate the list and print the (a) and print the output as

1,2,3