Le Fri, 11 Oct 2013 14:24:29 +0200,
Stefan Krah <ste...@bytereef.org> a écrit :
> Hi,
>
> recently there has been some talk about reducing import times. It
> seems that the current import strategy for C extensions (i.e.
> importing the extension at the bottom of the .py file) is quite slow:
>
>
> ====================
>
> import sys
>
> for i in range(10000):
> import decimal
> del sys.modules('decimal')
> del sys.modules('_decimal')
>
> ====================
Try the following:
$ ./python -m timeit -s "modname='decimal'; import sys" \
"__import__(modname); del sys.modules[modname]"
1000 loops, best of 3: 2.21 msec per loop
$ ./python -m timeit -s "modname='_decimal'; import sys" \
"__import__(modname); del sys.modules[modname]"
10000 loops, best of 3: 112 usec per loop
Now compare with the time taken to simply find the module loader:
$ ./python -m timeit -s "modname='_decimal'; import importlib" \
"importlib.find_loader(modname)"
10000 loops, best of 3: 87.2 usec per loop
So find_loader() is the bigger contributor here. Note that find_loader()
can have varying performance:
$ touch empty.py
$ ./python -m timeit -s "modname='empty'; import importlib" \
"importlib.find_loader(modname)"
10000 loops, best of 3: 24.4 usec per loop
When trying to improve import performance, I noticed that merely
diagnosing the bottlenecks is not always easy.
Regards
Antoine.
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