return statement in functions
hokiegal99 at hotmail.com
Tue Dec 23 14:42:37 CET 2003
Francis Avila wrote:
> hokiegal99 wrote in message
> <93f5c5e9.0312221718.23e42dac at posting.google.com>...
>>I was told earlier (w/o explanation) that functions should return
>>something. I was under the impression that it was OK with Python to
>>leave the return statement off.
> Functions return something in Python, by definition. If you leave the
> return statement off, Python inserts an implicit 'return None' to the end of
> the text of your function.
>>Could someone enlighten me on why or
>>why not to use a return statement when defining functions?
> This is a philosophic question. The final end of a function is to take
> input and return output which is somehow based upon that input. The
> functional *construct* can be abused every which way (often validly) to
> violate any part of that statement: it can take arguments which don't
> matter; it can return things which are unrelated to the arguments; it can
> have all sorts of side effects that the caller isn't interested in, etc.
>>the bit of code I was told should return something:
>> file_count = 0
>> dir_count = 0
>> for root, dirs, files in os.walk(path):
>> file_count += len(files)
>> dir_count += len(dirs)
>> print "Number of Files Examined: ", file_count
>> print "Number of Folders Examined: ", dir_count
>> print "Total Number of FS Objects:", file_count + dir_count
> The code is in poor style simply because it does multiple things at once in
> a way that is not terribly modular: namely, it does file/dir counts, and it
> prints results.
> Better would be this:
> def fs_object_count(path):
> """Return (numdirs, numfiles) in path and its subdirectories."""
> file_count = 0
> dir_count = 0
> for root, dirs, files in os.walk(path):
> file_count += len(files)
> dir_count += len(dirs)
> return dir_count, file_count
> dn, fn = fs_object_count('mypath')
> print "Number of Files:", fn
> print "Number of Directories:", dn
> print "Total:", fn+dn
> You can have more complex/prettier output logic if you want, but the point
> is to make your functions as general as possible, while doing only one
> thing. (And that's not a contradiction!)
> Francis Avila
This was very helpful to me. Thank you for taking the time to explain it!!!
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