[Python-checkins] cpython (2.7): Closes #10031: overhaul the "imports" section of the programming FAQ.

[georg.brandl]

https://hg.python.org/cpython/rev/9d321235f1f9
changeset:   92850:9d321235f1f9
branch:      2.7
parent:      92844:af18f1e1ade2
user:        Georg Brandl <georg at python.org>
date:        Mon Oct 06 16:21:08 2014 +0200
summary:
  Closes #10031: overhaul the "imports" section of the programming FAQ.

Remove the advice to never use relative imports.
Remove the advice to locally import modules in __init__, it is a strange practice.
Remove the advice to use "from ... import *" with some modules.

files:
  Doc/c-api/type.rst      |   2 +-
  Doc/faq/programming.rst |  20 +++++---------------
  2 files changed, 6 insertions(+), 16 deletions(-)


diff --git a/Doc/c-api/type.rst b/Doc/c-api/type.rst
--- a/Doc/c-api/type.rst
+++ b/Doc/c-api/type.rst
@@ -72,7 +72,7 @@
    .. versionadded:: 2.2
 
    This function only checks for actual subtypes, which means that
-   :meth:`~type.__subclasscheck__` is not called on *b*.  Call
+   :meth:`~class.__subclasscheck__` is not called on *b*.  Call
    :c:func:`PyObject_IsSubclass` to do the same check that :func:`issubclass`
    would do.
 
diff --git a/Doc/faq/programming.rst b/Doc/faq/programming.rst
--- a/Doc/faq/programming.rst
+++ b/Doc/faq/programming.rst
@@ -438,9 +438,8 @@
 -----------------------------------------------------------
 
 In general, don't use ``from modulename import *``.  Doing so clutters the
-importer's namespace.  Some people avoid this idiom even with the few modules
-that were designed to be imported in this manner.  Modules designed in this
-manner include :mod:`Tkinter`, and :mod:`threading`.
+importer's namespace, and makes it much harder for linters to detect undefined
+names.
 
 Import modules at the top of a file.  Doing so makes it clear what other modules
 your code requires and avoids questions of whether the module name is in scope.
@@ -454,11 +453,10 @@
    directory) -- e.g. mx.DateTime, ZODB, PIL.Image, etc.
 3. locally-developed modules
 
-Never use relative package imports.  If you're writing code that's in the
-``package.sub.m1`` module and want to import ``package.sub.m2``, do not just
+Only use explicit relative package imports.  If you're writing code that's in
+the ``package.sub.m1`` module and want to import ``package.sub.m2``, do not just
 write ``import m2``, even though it's legal.  Write ``from package.sub import
-m2`` instead.  Relative imports can lead to a module being initialized twice,
-leading to confusing bugs.  See :pep:`328` for details.
+m2`` or ``from . import m2`` instead.
 
 It is sometimes necessary to move imports to a function or class to avoid
 problems with circular imports.  Gordon McMillan says:
@@ -490,14 +488,6 @@
 couple of dictionary lookups.  Even if the module name has gone out of scope,
 the module is probably available in :data:`sys.modules`.
 
-If only instances of a specific class use a module, then it is reasonable to
-import the module in the class's ``__init__`` method and then assign the module
-to an instance variable so that the module is always available (via that
-instance variable) during the life of the object.  Note that to delay an import
-until the class is instantiated, the import must be inside a method.  Putting
-the import inside the class but outside of any method still causes the import to
-occur when the module is initialized.
-
 
 Why are default values shared between objects?
 ----------------------------------------------

-- 
Repository URL: https://hg.python.org/cpython