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Groups > comp.lang.python > #57990

RE: Using "with open(filename, 'ab'):" and calling code only if the file is new?

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>     with open(self.full_path, 'r') as input, open(self.output_csv, 'ab') as
> output:
>         fieldnames = (...)
>         csv_writer = DictWriter(output, filednames)
>         # Call csv_writer.writeheader() if file is new.
>         csv_writer.writerows(my_dict)
> 
> I'm wondering what's the best way of calling writeheader() only if the file is
> new?
> 
> My understanding is that I don't want to use os.path.exist(), since that opens
> me up to race conditions.

What stops you from checking before and setting a flag?

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Using "with open(filename, 'ab'):" and calling code only if the file is new? Victor Hooi <victorhooi@gmail.com> - 2013-10-29 18:02 -0700
  RE: Using "with open(filename, 'ab'):" and calling code only if the file is new? "Joseph L. Casale" <jcasale@activenetwerx.com> - 2013-10-30 01:42 +0000
  RE: Using "with open(filename, 'ab'):" and calling code only if the file is new? Dave Angel <davea@davea.name> - 2013-10-30 02:13 +0000
  RE: Using "with open(filename, 'ab'):" and calling code only if the file is new? "Joseph L. Casale" <jcasale@activenetwerx.com> - 2013-10-30 02:55 +0000
    Re: Using "with open(filename, 'ab'):" and calling code only if the file is new? Victor Hooi <victorhooi@gmail.com> - 2013-10-29 20:22 -0700
  Fwd: Using "with open(filename, 'ab'):" and calling code only if the file is new? Zachary Ware <zachary.ware+pylist@gmail.com> - 2013-10-29 22:28 -0500
  Re: Using "with open(filename, 'ab'):" and calling code only if the file is new? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-10-30 08:53 +0100
  Re: Using "with open(filename, 'ab'):" and calling code only if the file is new? Neil Cerutti <neilc@norwich.edu> - 2013-10-30 13:23 +0000

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