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Re: Best use of "open" context manager (Posting On Python-List Prohibited)

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On 6 Jul 2024 11:46:33 GMT, Stefan Ram wrote:

>>but this of course does not work because by the time we get to "for ln
>>in f:" the file has been closed so we get ValueError: I/O operation on
>>closed file
> 
> try:
>     f = open( FileName )
> except FileNotFoundError:
>     print( f"File {FileName} not found" )
>     sys.exit()
> else:
>     with f:
>         # put this into a separate function if it gets too long here.
>         for ln in f:
>             print( "I do a lot of processing here" )
>             # Many lines of code here .....

    f = open(filename, "rt")
    for ln in f :
        ... do your processing ...

1) Let the error exception be reported directly, whether it’s “file not 
found”, or “permission error”, or some other reason; why bother to handle 
it when you don’t even know what to do anyway?
2) Notice that a file open for reading automatically gets closed when it 
goes out of scope (feature of CPython and all the other good 
implementations).

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Best use of "open" context manager Rob Cliffe <rob.cliffe@btinternet.com> - 2024-07-06 11:49 +0100
  Re: Best use of "open" context manager (Posting On Python-List Prohibited) Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-07 03:49 +0000

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