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Date: Wed, 16 Jul 2014 21:54:21 +1000
Subject: Re: Python 3 is killing Python
From: Chris Angelico <rosuav@gmail.com>
Cc: "python-list@python.org" <python-list@python.org>
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Xref: csiph.com comp.lang.python:74548

On Wed, Jul 16, 2014 at 9:35 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> What I had in mind was for print to open the file in append mode, write,
> then close the file.

Ahh, okay. Very different from what I thought you were talking about,
and distinctly different in behaviour from REXX :)

In that case, it avoids the problems that I described, at the expense
of being potentially an attractive nuisance - imagine code like this:

for line in open("input.txt"):
    print(transform(line), file="output.txt")

Looks like a really nice clean way to process a file, right? But it's
going to be horrendously slow.

Actually, this could be quite reasonably added as a feature of
print(). Could be monkey-patched in fairly easily

_origprint = print
def print(*a, **kw):
    if isinstance(kw.get("file"), (str, bytes)):
        with open(kw["file"], 'a') as f:
            kw["file"] = f
            _origprint(*a, **kw)
    else:
        _origprint(*a, **kw)

And it'd have its uses. The only risk would be if there's a file-like
object that's a subclass of either str or bytes, which admittedly *is*
theoretically possible...

ChrisA