Subclassing file class

[David Vaughan]

I'm using v2.3, and trying to write to text files, but with a maximum
line length. So, if a line is getting too long, a suitable ' '
character is replaced by a new line. I'm subclassing the file class,
and, as long as I just use the write method, this works fine. But
"print >>" doesn't behave as I want:

class max_width_file(file):
def write(self, txt):
print "In max_width_file's write method."
fout = max_width_file('foo.txt', 'w')
print >> fout, 'bar'
fout.close()

bypasses my write method and prints 'bar' directly to the file. That
isn't the behaviour I inferred from

http://docs.python.org/ref/print.html

How do I intercept "print >>"? Has anyone already implemented this?
And should the documentation be changed?

Any help very welcome.
David



David Vaughan
Structural Analyst
for Gifford

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[Michael Hudson]

I'm using v2.3, and trying to write to text files, but with a maximum
line length. So, if a line is getting too long, a suitable ' '
character is replaced by a new line. I'm subclassing the file class,
and, as long as I just use the write method, this works fine. But
"print >>" doesn't behave as I want:

You'll almost certainly be happier implementing a 'file-like object'
that does what you want than subclassing file.

Cheers,
mwh

 

[Christos TZOTZIOY Georgiou]

I'm using v2.3, and trying to write to text files, but with a maximum
line length. [snip]

Apart from any other advices you get, you might want to consider the
textwrap module.