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argparse/python - how to specify order of argument parsing?

+1 vote
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When using argparse, is there a way to specify in what order arguments get parsed? I am writing a script whose parameters can be modified in the following order:

Defaults -> config file -> command-line switches.

However, I want to give the option of specifying a config file using a command line switch as well, so logically, that file should be parsed before any other arguments are applied. However, it seems that parse_args() parses arguments in the order they're given, so if the config file switch is not given first, the config file will overwrite whatever was in the command-line switches, which should have higher priority.

posted Aug 31, 2013 by Abhay Kulkarni

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1 Answer

+1 vote

While I haven't come up with a good solution using argparse/optparse alone, I've found that it's easier (for processing) to specify the config file as an environment variable. So rather than doing

my_prog.py -c /path/to/config.ini arg1 arg2 ...

I just do

 MY_PROG_CONF=/path/to/config.ini my_prog.py arg1 arg2 ...

...at least on *nix systems; on Win32, it's

 c:temp> set MY_PROG_CONF=c:pathtoconfig.ini
 c:temp> python my_prog.py arg1 arg2 ...

Then you just intercept the config-file name from os.environ:

 config_file = os.environ.get("MY_PROG_CONF", default_ini_location)
answer Aug 31, 2013 by Sheetal Chauhan
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