[Tutor] reading lines from a list of files

[Alex Kleider]

On 2015-05-13 23:24, Danny Yoo wrote:
>> As a follow up question:
>> The following seems to work-
>> 
>>     for f_name in list_of_file_names:
>>         for line in open(f_name, 'r'):
>>             process(line)
>> 
>> but should I be worried that the file doesn't get explicitly closed?
> 
> 
> It depends on context.  Personally, I'd write it with the 'with' to
> make it very clear that the loop will manage its resource.  That being
> said, it sounds like there might be concerned about the nesting.
> We're nesting three or four levels deep, at the very least!
> 
> I'd agree with that.  Because of this, it might be worthwile to
> consider refactoring the processing of the file in a separate
> function, something like this:
> 
> ###############################
> def processFile(f):
>     for line in f:
>         ...
> 
> for f_name in list_of_file_names:
>      with open(f_name, 'r') as f:
>          processFile(f)
> ###############################
> 
> The primary reason is to reduce the nesting.  But there's also a
> potential side benefit: processFile() has a better chance of being
> unit-testable, since we can pass in instances of other file-like
> objects, such as io.StringIO(), to spot-check the behavior of the
> process.

Thanks, Danny.  This is particularly germane since the issue has come up 
in the
midst of my first attempt to do test driven development.  I'll try 
refactoring per
your suggestion.