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On-demand imports, taken from mercurial

Project description


Delays loading of modules until they are actually used. Perfect for Python apps that need to be snappy like command-line utils. Source-code derived from mercurial.

To enable, write

import demandimport; demandimport.enable()

Imports of the following form will be delayed

import a, b.c
import a.b as c
from a import b, c # a will be loaded immediately, though

These imports with not be delayed

from a import *
b = __import__(a)

Delayed loading will confuse some third-party modules. In that case you can disable the delay for just that module. For example


There are also versions that can be used with with

with demandimport.enabled():
   # do something
   with demandimport.disabled():
      import troublesome.module
   with demandimport.ignored('test'):
      import other.troublemaker


To install demandimport, simply run:

pip install demandimport


Matt Mackall <> is the original author of the module in Mercurial on which this module is based. Bas Westerbaan <> maintains it now.

py-demandimport Changelog

0.3.4 (2017-06-08)

  • Python 3.6

  • Add sip to the default ignore list. #6

0.3.3 (2016-10-20)

  • Add is_loaded and is_proxy. Thanks-to:

0.3.2 (2015-12-22)

  • Fixed issue #2: import a.b.c will incorrectly try to import b.c

0.3.1 (2015-12-21)

  • Relicense GPL version 2 or later (GPLv2+)

0.3.0 (2015-12-21)

  • Do not delay ImportError in a special case.

  • Add optional logging (for debugging)

  • Fixed issue #1: import a.b in a module a.c was incorrectly executed as a relative import c.

  • Improve thread safety

0.2.2 (2015-12-05)

  • Moved to zest.releaser

  • Add some basic unittests

  • Python 3 support

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