will with sys.stdout as f: close sys.stdout?

[Skaperen]

i have a big block of code the i do not want to duplicate. in one case i want the block to be done with f as an opened file that gets closed at the end. in the other case it should output to stdout without closing stdout. at first i did it like this:

    for name in all_the_names:
        with stdout if 'stdout' in options else open(f'{name}.log','w') as f:
            ...
            print(...,file=f) # many lines of code here, do not copy
            ...

then i realized that the with might cause stdout to be closed. would that really happen? if so, how can i avoid that?

[Gribouillis]

A contextmanager should do the trick (to be tested)

from contextlib import contextmanager
import sys

@contextmanager
def outfile(name, use_stdout):
    if use_stdout:
        yield sys.stdout
    else:
        with open(f'{name}.log', 'w') as f:
            yield f

for name in all_the_names:
    with outfile(name, stdout in options) as f:
        print('Spam', file=f)

[Skaperen]

could that work for this other thing i want do? i want to be able to open and write a file with a temporary name of my choice and when with closes it, it also gets renamed to the permanent name.

for name in names:
    t = int(time.time()*3906250)
    with tmpopen(f'{name}-(t)',name,'w') as f
        print('#!/usr/bin/env python3',file=f)
        print('# put your code here:',file=f)

[Gribouillis]

could that work for this other thing i want do?

Of course it would, you only need to rename the file after the 'with open...' block in the contextmanager. But I think we already discussed this problem in the forum and we wrote a solution somewhere.

[Skaperen]

i want to do it within the with statement so that it is sure to happen (or at least be attempted). sure, i can do it after the with. i can close the file after the with, too. the justification for using with to do a close ... i want to use for doing the rename, too. so i would expect a method that returns an object with a context manager that takes care of both the close and the rename.

[Gribouillis]

It is after the with statement in the context manager but it is included in the with statement for the code that uses the contextmanager.

[Skaperen]

i thought with called some special method on the file(-like) object used in the with statement that does a close on the file.

[Gribouillis]

i thought with called some special method on the file(-like) object used in the with statement that does a close on the file.

In the statement

with foo as bar:
    spam()

bar is not foo, it is the value returned by foo.__enter__() which can be anything, including a file object. At the end of the with statement's execution, no method is called on bar, but the method foo.__exit__() is called.

It often happens that foo and bar are the same object, for example when foo is the result of a call to open(). The __exit__() method on a file object calls the close() method, but in general you can program whatever behaviour at a block's exit, even if bar is a file object.

[DeaD_EyE]

The use of a context manager together with sys.stdout does not make much sense, because the fd is open until the program ends.

import os


with os.fdopen(sys.stdout.fileno(), 'w', closefd=False) as fd:
    fd.write('Hello World\n')

# is still open
sys.stdout.write('Hello World\n')

[Gribouillis]

It makes sense here because Skaperen wants the same client code whether he uses stdout or a regular file. It's an API normalization.