Steven D'Aprano steve+comp.lang.pyt...@pearwood.info via python.org
8:56 PM (12 hours ago) wrote:
> Write a helper function:
>
> def process(opener):
> with opener('blah.txt', 'rb') as f:
> for line in f:
> print(line)
As another option, you can enter the context manager after you decide.
try:
f = gzip.open('blah.txt', 'rb')
except IOError:
f = open('blah.txt', 'rb')
with f:
# processing
for line in f:
print(line)
contextlib.ExitStack was designed to handle cases where entering
context is optional, and so also works for this use case.
with contextlib.ExitStack() as stack:
try:
f = gzip.open('blah.txt', 'rb')
except IOError:
f = open('blah.txt', 'rb')
stack.enter_context(f)
for line in f:
print(line)
--
Neil Cerutti
On Tue, Nov 19, 2013 at 8:56 PM, Steven D'Aprano
<steve+comp.lang.pyt...@pearwood.info> wrote:
> On Tue, 19 Nov 2013 16:30:46 -0800, Victor Hooi wrote:
>
>> Hi,
>>
>> Is either approach (try-excepts, or using libmagic) considered more
>> idiomatic? What would you guys prefer yourselves?
>
> Specifically in the case of file types, I consider it better to use
> libmagic. But as a general technique, using try...except is a reasonable
> approach in many situations.
>
>
>> 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)?
>
> Write a helper function:
>
> def process(opener):
> with opener('blah.txt', 'rb') as f:
> for line in f:
> print(line)
>
>
> try:
> process(gzip.open)
> except IOError:
> process(open)
>
>
> If you have many different things to try:
>
>
> for opener in [gzip.open, open, ...]:
> try:
> process(opener)
> except IOError:
> continue
> else:
> break
>
>
>
> [...]
>> 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?
>
> *shrug*
>
> Read the docs of python-magic. Do they offer a programmable API? If not,
> that kinda sucks.
>
>
>
> --
> Steven
> --
> https://mail.python.org/mailman/listinfo/python-list
--
Neil Cerutti <mr.cerutti+pyt...@gmail.com>
--
https://mail.python.org/mailman/listinfo/python-list
