[Tutor] scratching my head
crk at godblessthe.us
Mon Aug 3 00:28:06 CEST 2015
> -----Original Message-----
> From: Tutor [mailto:tutor-bounces+crk=godblessthe.us at python.org] On
> Behalf Of Alan Gauld
> Sent: Sunday, August 02, 2015 3:01 PM
> To: tutor at python.org
> Subject: Re: [Tutor] scratching my head
> On 02/08/15 22:44, Clayton Kirkwood wrote:
> > for dir_path, directories, files in os.walk(main_dir):
> > for file in files:
> > # print( " file = ", file)
> > # if( ("(\.jpg|\.png|\.avi|\.mp4)$") not in file.lower() ):
> Python sees that as a single string. That string is not in your filename.
> > # if( (".jpg" or ".png" or ".avi" or ".mp4" ) not in
> Python sees that as a boolean expression so will try to work it out as a
> True/False value. Since a non empty string is considered True and the
> True expression makes an OR opeation True overall it returns ".jpg" and
> if it is not in the filename.
> > #except by the drudgery below. I should be able to just have a list,
> > maybe from a file, that lists all
> You might think so but that's not how 'in' works.
> But you could use a loop:
> found = False
> for s in (".jpg",".png",".avi",".mp4"):
> found = test or (s in file.lower()) if not found: ...
The for is much better and it's able to get input from a file. I would think
Python more sensible if something like my commented one would work. That
would make more sense to me.
> > if( ".jpg" not in file.lower() and
> > ".png" not in file.lower() and
> > ".avi" not in file.lower() and
> > ".mp4" not in file.lower() ):
> Whether that's any better than your combined test is a moot point.
> Alan G
> Author of the Learn to Program web site
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