On 04/30/2015 04:06 AM, Cecil Westerhof wrote:
Op Thursday 30 Apr 2015 09:33 CEST schreef Chris Angelico:
On Thu, Apr 30, 2015 at 4:27 PM, Cecil Westerhof <ce...@decebal.nl> wrote:
with open("input.cpp") as f:
lines = f.readlines()
print(lines[7])
Is the following not better:
print(open('input.cpp', 'r').readlines()[7])
Time is the same (about 25 seconds for 100.000 calls), but I find
this more clear.
The significant difference is that the 'with' block guarantees to
close the file promptly. With CPython it probably won't make a lot
of difference, and in a tiny script it won't do much either, but if
you do this on Jython or IronPython or MicroPython or some other
implementation, it may well make a gigantic difference - your loop
might actually fail because the file's still open.
I thought that in this case the file was also closed. But if that is
not the case I should think about this when I switch to another
version as CPython.
I wrote a module where I have:
def get_indexed_message(message_filename, index):
"""
Get index message from a file, where 0 gets the first message
"""
return open(expanduser(message_filename),
'r').readlines()[index].rstrip()
But this can be used by others also and they could be using Jython or
another implementation. So should I rewrite this and other functions?
Or would it be OK because the open is in a function?
No, it's not going to close the file just because the open is in a
function. The "with" construct was designed to help solve exactly this
problem. Please use it.
--
DaveA
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