If - Or statements

[rzed]

Ognjen Bezanov <ognjen at mailshack.com> wrote in
news:mailman.483.1117877861.18027.python-list at python.org: 

> Robert Kern wrote:
> 
>> Ognjen Bezanov wrote:
>>
>>> Another newbie-ish question.
>>>
>>> I want to create an if statement which will check if a
>>> particular variable matches one of the statements, and willl
>>> execute the statement if the variable matches any of the
>>> statements. 
>>>
>>> I have tried the following (the pass is just used for testing)
>>>
>>>
>>> if ext[1] == "mp3" or ext[1] == "mp4" or ext[1] == "ogg" or
>>> ext[1] == "aac" or ext[1] != "wma":
>>>        print "we have a valid extension: " + ext[1] #here
>>>        would go the 
>>> code for decoding the above
>>>        pass
>>
>>
>> It works fine for me. Could you post the smallest complete
>> program (one that defines ext) that displays the behavior and
>> its entire output? 
>>
>> As an aside, is 'ext[1] != "wma"' correct or should it be ==?
>> As written, you could collapse the whole thing to 'if ext[1] !=
>> "wma":' but I presume it is a typo.
>>
> filelist = os.listdir('/mnt/cdrom/') #get a list of files from
> the cdrom drive
>         for thefile in filelist[:]:   #for each file in the
>         filelist 
>             if thefile.find(".") != -1:   #if the file has an
>             extenstion 
> at all
>                 ext = thefile.split('.') #get the file extension
>                 ext[1] =  ext[1].lower() #convert to lowercase
>                 print ext[1] #debugging, to see the variable
>                 before 
> passed to if statement
> 
>                 if ext[1] == "mp3" or ext[1] == "mp4" or ext[1]
>                 == "ogg" 
> or ext[1] == "aac" or ext[1] == "wma":
>                     print "we have a valid extension: " + ext[1]
>                     #here 
> would go the code for decoding the above
>                     pass

Though this may sidetrack the issue, another way of doing multiple 
checks like that is to make a list and check for inclusion in the 
list. Something like this:
exts = ['mp3','mp4','ogg','aac','wma']
if ext[1] not in exts:
    	# do whatever

or
if ext[1] in exts:
    	print 'we have a valid extension:',ext[1]

It's easier to add to the list than to add another explicit test, 
particularly if the tests occur in several places.
-- 
rzed