argparse and filetypes

[Alex Willmer]

On Mar 22, 2:06 pm, Bradley Hintze <bradle... at aggiemail.usu.edu>
wrote:
> I just started with argparse. I want to simply check the extension of
> the file that the user passes to the program. I get a ''file' object
> has no attribute 'rfind'' error when I use
> os.path.splitext(args.infile).  Here is my code.
>
> import argparse, sys, os
>
> des = 'Get restraint definitions from probe.'
> parser = argparse.ArgumentParser(description=des)
> parser.add_argument('infile', nargs='?', type=argparse.FileType('r'))
> # parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'),
>                    # default=sys.stdout)
>
> args = parser.parse_args()
> # print args.infile.readlines()
> print basename, extension = os.path.splitext(args.infile)

Because you specified type=argparse.FileType('r') argparse has created
args.infile as a file object (e.g. open('/some/path/data.dat', 'r')),
not as a string containing the path. So type(args.infile) ==
type(file) and args.infile.readlines() returns the contents of that
file.

If you wish to check the file extension of the path in question I
suggest you remove type=argparse.FileType('r'), argparse will create
args.infile as a string containing that path. To open the file call
open(args.infile, 'r'), this will return the file object.