Smith, Jeff wrote:
> At least with Python there's only one obvious way to do something :-)
Yeah, right. A couple of minutes reading comp.lang.python will disabuse
you of that notion :-)
>
> I'll see your simplification and raise (or lower) you a line.
>
> Why not simply:
>
> for item in file('hosts.txt'):
> tn = telnetlib.Telnet(item.strip())
If you are willing to depend on the runtime to close the file that is
fine. If you want to close it yourself you have to keep a reference to
the open file.
For short Python scripts I usually allow the runtime to close the file.
For longer programs and anything written in Jython (which has different
garbage collection behaviour) I usually use an explicit close().
Kent
>
> Jeff
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
> Behalf Of Kent Johnson
> Sent: Wednesday, May 10, 2006 5:52 AM
> Cc: tutor@python.org
> Subject: Re: [Tutor] For loop question
>
>
> w chun wrote:
>> another thing is that if the host file is large, you may wish to
>> iterate through the file one line at a time with a list comprehension
>> to do the stripping for you:
>>
>> HostFile = open("hosts.txt", 'r')
>> for item in [x.strip() for x in HostFile]:
>> :
>
> Why is this better when the file is large? It still creates a list with
> all lines in it.
>> if you are using Python 2.4+, you can come up with an even better
>> solution by using a generator expression that does lazier, ad hoc
>> evaluation:
>>
>> HostFile = open("hosts.txt", 'r')
>> for item in (x.strip() for x in HostFile):
>> :
>>
>> this one will read and strip one line from the file as you process it
>> while the previous solution still needs to come up with the entire
>> list of stripped hosts before the for-loop can begin.
>
> I would use this, it avoids reading the entire file at once and IMO is
> clear and straightforward:
> HostFile = open('hosts.txt')
> for item in HostFile:
> item = item.strip()
> ...
>
> or even
> HostFile = open('hosts.txt')
> for item in HostFile:
> tn = telnetlib.Telnet(item.strip())
> ...
>
> Kent
>
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>
>
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