Python: Combining string and lists

Question

I have a list of counters

counters = ['76195087', '963301809', '830123644', '60989448', '0', '0', '76195087', '4006066839', '390361581', '101817210', '0', '0']

and I would like to create a string using some of these counters....

cmd = 'my_command' + counters[0:1]

But I find that I am unable to concatenate strings and lists.

What I must have at the end is a string that looks like this:

my_command 76195087

How do I get these numbers out of their list and get them to behave like strings?

Answer 1

You can join strings in a list with, well, join:

cmd = 'my_command' + ''.join(counters[:1])

But you shouldn't construct a command like that in the first place and give it to os.popen or os.system. Instead, use the subprocess module, which handles the internals (and escapes problematic values):

import subprocess
# You may want to set some options in the following line ...
p = subprocess.Popen(['my_command'] + counters[:1])
p.communicate()

Answer 2

If you just want a single element of the list, just index that element:

cmd = 'my_command ' + counters[0]

If you want to join several elements, use the 'join()' method of strings:

cmd = 'my_command ' + " ".join(counters[0:2]) # add spaces between elements