Using try-catch to handle multiple possible file types?

Victor Hooi victorhooi at gmail.com
Wed Nov 20 01:30:46 CET 2013


Hi,

Is either approach (try-excepts, or using libmagic) considered more idiomatic? What would you guys prefer yourselves?

Also, is it possible to use either approach with a context manager ("with"), without duplicating lots of code?

For example:

try:
	with gzip.open('blah.txt', 'rb') as f:
		for line in f:
			print(line)
except IOError as e:
	with open('blah.txt', 'rb') as f:
		for line in f:
			print(line)

I'm not sure of how to do this without needing to duplicating the processing lines (everything inside the with)?

And using:

try:
	f = gzip.open('blah.txt', 'rb')
except IOError as e:
	f = open('blah.txt', 'rb')
finally:
	for line in f:
		print(line)

won't work, since the exception won't get thrown until you actually try to open the file. Plus, I'm under the impression that I should be using context-managers where I can.

Also, on another note, python-magic will return a string as a result, e.g.:

gzip compressed data, was "blah.txt", from Unix, last modified: Wed Nov 20 10:48:35 2013

I suppose it's enough to just do a?

    if "gzip compressed data" in results:

or is there a better way?

Cheers,
Victor

On Tuesday, 19 November 2013 20:36:47 UTC+11, Mark Lawrence  wrote:
> On 19/11/2013 07:13, Victor Hooi wrote:
> 
> >
> 
> > So basically, using exception handling for flow-control.
> 
> >
> 
> > However, is that considered bad practice, or un-Pythonic?
> 
> >
> 
> 
> 
> If it works for you use it, practicality beats purity :)
> 
> 
> 
> -- 
> 
> Python is the second best programming language in the world.
> 
> But the best has yet to be invented.  Christian Tismer
> 
> 
> 
> Mark Lawrence



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