how to join array of integers?

[Summercool]

i think in Ruby, if you have an array (or list) of integers

foo = [1, 2, 3]

you can use foo.join(",") to join them into a string "1,2,3"

in Python... is the method to use  ",".join() ?  but then it must take
a list of strings... not integers...

any fast method?