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Diffstat (limited to 'Doc/tutorial/classes.rst')
| -rw-r--r-- | Doc/tutorial/classes.rst | 33 |
1 files changed, 27 insertions, 6 deletions
diff --git a/Doc/tutorial/classes.rst b/Doc/tutorial/classes.rst index d9e2f46..b9db87b 100644 --- a/Doc/tutorial/classes.rst +++ b/Doc/tutorial/classes.rst @@ -124,6 +124,8 @@ 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 @@ -137,12 +139,15 @@ 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 normally 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. +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.) The :keyword:`global` statement can be used to indicate that particular variables live in the global scope and should be rebound there; the @@ -466,6 +471,9 @@ classes defined in it. Usually, the class containing the method is itself defined in this global scope, and in the next section we'll find some good reasons why a method would want to reference its own class! +Each value is an object, and therefore has a *class* (also called its *type*). +It is stored as ``object.__class__``. + .. _tut-inheritance: @@ -515,6 +523,19 @@ arguments)``. This is occasionally useful to clients as well. (Note that this only works if the base class is defined or imported directly in the global scope.) +Python has two builtin functions that work with inheritance: + +* Use :func:`isinstance` to check an object's type: ``isinstance(obj, int)`` + will be ``True`` only if ``obj.__class__`` is :class:`int` or some class + derived from :class:`int`. + +* Use :func:`issubclass` to check class inheritance: ``issubclass(bool, int)`` + is ``True`` since :class:`bool` is a subclass of :class:`int`. However, + ``issubclass(unicode, str)`` is ``False`` since :class:`unicode` is not a + subclass of :class:`str` (they only share a common ancestor, + :class:`basestring`). + + .. _tut-multiple: |