CSV performance

[Peter Otten]

Lawrence D'Oliveiro wrote:

> In message <gt47lc$kar$03$1 at news.t-online.com>, Peter Otten wrote:
> 
>> gc.disable()
>> # create many small objects that you want to keep
>> gc.enable()
> 
> Every time I see something like this, I feel the urge to save the previous
> state and restore it afterwards:
> 
>     save_enabled = gc.isenabled()
>     gc.disable()
>     # create many small objects that you want to keep
>     if save_enabled :
>         gc.enable()
>     #end if
> 
> Maybe that's just me. :)

There's probably someone out there who does nested GC states on a daily 
basis ;)

When I see the sequence

save state
change state
do something
restore state

I feel compelled to throw in a try ... finally

save state
try:
    change state
    do something
finally:
    restore state

which in turn leads to

import gc

from contextlib import contextmanager

@contextmanager
def gcdisabled():
    was_enabled = gc.isenabled()
    gc.disable()
    try:
        yield
    finally:
        if was_enabled:
            gc.enable()
        
if __name__ == "__main__":
    try:
        with gcdisabled():
            assert not gc.isenabled()
            try:
                with gcdisabled():
                    assert not gc.isenabled()
                    1/0
            finally:
                assert not gc.isenabled()
    except ZeroDivisionError:
        pass
    assert gc.isenabled()

So far, so good. But is it thread-safe?

I think you are beginning to see why the original suggestion was my best 
option...

Peter