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Little clarification of assignments.

This commit is contained in:
Georg Brandl 2008-03-06 07:22:09 +00:00
parent 70992c3c83
commit 26bab5f92a
1 changed files with 11 additions and 8 deletions
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Doc/tutorial/classes.rst
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@ -123,6 +123,8 @@ found outside of the innermost scope are read-only (an attempt to write to such
a variable will simply create a *new* local variable in the innermost scope,
leaving the identically named outer variable unchanged).
.. XXX mention nonlocal
Usually, the local scope references the local names of the (textually) current
function. Outside functions, the local scope references the same namespace as
the global scope: the module's namespace. Class definitions place yet another
@ -136,14 +138,15 @@ language definition is evolving towards static name resolution, at "compile"
time, so don't rely on dynamic name resolution! (In fact, local variables are
already determined statically.)
A special quirk of Python is that assignments always go into the innermost
scope. Assignments do not copy data --- they just bind names to objects. The
same is true for deletions: the statement ``del x`` removes the binding of ``x``
from the namespace referenced by the local scope. In fact, all operations that
introduce new names use the local scope: in particular, import statements and
function definitions bind the module or function name in the local scope. (The
:keyword:`global` statement can be used to indicate that particular variables
live in the global scope.)
A special quirk of Python is that -- if no :keyword:`global` or
:keyword:`nonlocal` statement is in effect -- assignments to names always go
into the innermost scope. Assignments do not copy data --- they just bind names
to objects. The same is true for deletions: the statement ``del x`` removes the
binding of ``x`` from the namespace referenced by the local scope. In fact, all
operations that introduce new names use the local scope: in particular, import
statements and function definitions bind the module or function name in the
local scope. (The :keyword:`global` statement can be used to indicate that
particular variables live in the global scope.)
.. _tut-firstclasses: