python - argparse fails when called from unittest test -

in file (say parser.py) have:

import argparse  def parse_cmdline(cmdline=none):     parser = argparse.argumentparser()     parser.add_argument('--first-param',help="does foo.")     parser.add_argument('--second-param',help="does bar.")      if cmdline not none:         args = parser.parse_args(cmdline)     else:         args = parser.parse_args()      return vars(args)  if __name__=='__main__':     print parse_cmdline() 

sure enough, when called command line works , give me pretty expect:

$ ./parser.py --first-param 123 --second-param 456 {'first_param': '123', 'second_param': '456'} 

but want unittest it, write test_parser.py file:

import unittest parser import parse_cmdline  class testparser(unittest.testcase):     def test_parse_cmdline(self):         parsed = parse_cmdline("--first-param 123 --second-param 456")          self.assertequal(parsed['first_param'],'123')         self.assertequal(parsed['second_param'],'456')  if __name__ == '__main__':     unittest.main() 

then following error:

usage: test_parser.py [-h] [--first-param first_param]                       [--second-param second_param] test_parser.py: error: unrecognized arguments: - - f r s t - p r m   1 2 3   - - s e c o n d - p r m   4 5 6 e ====================================================================== error: test_parse_cmdline (__main__.testparser) ---------------------------------------------------------------------- traceback (most recent call last):   file "./test_parser.py", line 8, in test_parse_cmdline     parsed = parse_cmdline("--first-param 123 --second-param 456")   file "/home/renan/test_argparse/parser.py", line 12, in parse_cmdline     args = parser.parse_args(cmdline)   file "/usr/lib/python2.7/argparse.py", line 1691, in parse_args     self.error(msg % ' '.join(argv))   file "/usr/lib/python2.7/argparse.py", line 2361, in error     self.exit(2, _('%s: error: %s\n') % (self.prog, message))   file "/usr/lib/python2.7/argparse.py", line 2349, in exit     _sys.exit(status) systemexit: 2  ---------------------------------------------------------------------- ran 1 test in 0.004s  failed (errors=1) 

as can seen, command line specified (--first-param 123 --second-param 456) became - - f r s t - p r m 1 2 3 - - s e c o n d - p r m 4 5 6 (each character separated space).

i don't understand why: doing wrong?

argparse wants "argument vector"—that is, list of separate arguments—not "command line" string.

and calling split won't solve things. example, command line shell:

python script.py --first-param '123 456' --second-param 789 

… correctly give 123 456 , 789, line of code:

parse_cmdline("--first-param '123 456' --second-param 789") 

will not; give '123 , 789, 456' doesn't know how deal with.

in fact, wrong:

parse_cmdline("--first-param '123' --second-param 789") 

… because you'll '123' instead of 123.

---

there 2 ways deal this.

first, if know you're trying pass, can pass list instead of string in first place, , don't need worry fiddly quoting , splitting details:

parse_cmdline(["--first-param", "123 456", "--second-param", "789"]) 

alternatively, if don't know you're trying pass, know looks on shell, can use shlex:

if cmdline not none:     args = parser.parse_args(shlex.split(cmdline)) 

… , python split command line same way standard unix shell, getting 123 456 single parameter.