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209
> factory, then yes, foo_factory is what I would use.
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To make startup time faster, we use the ``bzrlib.lazy_import`` module to
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delay importing modules until they are actually used. ``lazy_import`` uses
217
the same syntax as regular python imports. So to import a few modules in a
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from bzrlib.lazy_import import lazy_import
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lazy_import(globals(), """
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import bzrlib.transport
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At this point, all of these exist as a ``ImportReplacer`` object, ready to
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be imported once a member is accessed.
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Modules versus Members
241
~~~~~~~~~~~~~~~~~~~~~~
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While it is possible for ``lazy_import()`` to import members of a module
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wehn using the ``from module import member`` syntax, it is recommended to
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only use that syntax to load sub modules ``from module import submodule``.
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This is because variables and classes can frequently be used without
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needing a sub-member for example::
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lazy_import(globals(), """
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from module import MyClass
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return isinstance(x, MyClass)
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This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
257
object, rather than the real class.
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Passing to other variables
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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It also is incorrect to assign ``ImportReplacer`` objects to other variables.
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Because the replacer only knows about the original name, it is unable to
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replace other variables. The ``ImportReplacer`` class will raise an
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``IllegalUseOfScopeReplacer`` exception if it can figure out that this
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happened. But it requires accessing a member more than once from the new
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variable, so some bugs are not detected right away.
added
removed
HACKING
