On Mon, 2 Oct 2017 at 08:00 Christian Heimes <christ...@python.org> wrote:
> On 2017-10-02 15:26, Victor Stinner wrote: > > 2017-10-02 13:10 GMT+02:00 INADA Naoki <songofaca...@gmail.com>: > >> https://github.com/python/cpython/pull/3796 > >> In this PR, lazy loading only happens when uuid1 is used. > >> But uuid1 is very uncommon for nowdays. > > > > Antoine Pitrou added a new C extension _uuid which is imported as soon > > as uuid(.py) is imported. On Linux at least, the main "overhead" is > > still done on "import uuid". But Antoine change optimized a lot > > "import uuid" import time! > > > >> https://github.com/python/cpython/pull/3757 > >> In this PR, singledispatch is lazy loading types and weakref. > >> But singledispatch is used as decorator. > >> So if web application uses singledispatch, it's loaded before > preforking. > > > > While "import module" is fast, maybe we should use sometimes a global > > variable to cache the import. > > > > module = None > > def func(): > > global module > > if module is None: import module > > ... > > > > I'm not sure that it's possible to write an helper for such pattern. > > I would rather like to see a function in importlib that handles deferred > imports: > > modulename = importlib.deferred_import('modulename') > > def deferred_import(name): > if name in sys.modules: > # special case 'None' here > return sys.modules[name] > else: > return ModuleProxy(name) > > ModuleProxy is a module type subclass that loads the module on demand. > My current design for an opt-in lazy importing setup includes an explicit function for importlib that's mainly targeted for the stdlib and it's startup module needs, but could be used by others: https://notebooks.azure.com/Brett/libraries/di2Btqj7zSI/html/Lazy%20importing.ipynb .
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