Python with statement

Question

I'm reading PEP 343 and trying to make some examples. But it's not really clear to me now. Especially because I have an error:

>>> def f():
...     return 'f'
... 
>>> with f(): # or as f
...     print f() # or f
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: __exit__

Indeed, the function has no method __exit__. So how do you use the with statement?

it's useful for files as it calls the close automatically on __exit__ — jamylak
– jamylak, Commented Apr 28, 2012 at 21:56

mouad · Accepted Answer · 2012-04-28 21:55:58Z

3

If you want to use the with statement with a function you can use the contextlib.contextmanager decorator.

Example from the doc:

from contextlib import contextmanager

@contextmanager
def tag(name):
    print "<%s>" % name
    yield
    print "</%s>" % name

>>> with tag("h1"):
...    print "foo"
...
<h1>
foo
</h1>

answered Apr 28, 2012 at 21:55

mouad

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2 Comments

Jpaji Rajnish Over a year ago

The question was "How do you use the with statement?" not "Is there a library to use a with statement with functions?". I don't know why this answer was accepted.

mouad Over a year ago

@ zoogleflatt Because it answer OP X problem mywiki.wooledge.org/XyProblem :)

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