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| author | Guido van Rossum <guido@python.org> | 1997-09-11 22:54:49 (GMT) |
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| committer | Guido van Rossum <guido@python.org> | 1997-09-11 22:54:49 (GMT) |
| commit | 7ade6da8660a640651a7e37f1b77b2721045942b (patch) | |
| tree | 1741911913398e95f718c198c5a742c779bff499 /Demo/metaclasses | |
| parent | abffd00502fd0ac84392ec44cf4d4c3b8d2c4d0e (diff) | |
| download | cpython-7ade6da8660a640651a7e37f1b77b2721045942b.zip cpython-7ade6da8660a640651a7e37f1b77b2721045942b.tar.gz cpython-7ade6da8660a640651a7e37f1b77b2721045942b.tar.bz2 | |
As Paul Prescod pointed out, metaprogramming is really something
different (programs that write programs). We are dealing with
metaclasses here. So change the words slightly.
Diffstat (limited to 'Demo/metaclasses')
| -rw-r--r-- | Demo/metaclasses/index.html | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/Demo/metaclasses/index.html b/Demo/metaclasses/index.html index ee91f8f..52d52e9 100644 --- a/Demo/metaclasses/index.html +++ b/Demo/metaclasses/index.html @@ -1,18 +1,16 @@ <HTML> <HEAD> -<TITLE>Metaprogramming in Python 1.5</TITLE> +<TITLE>Metaclasses in Python 1.5</TITLE> </HEAD> <BODY BGCOLOR="FFFFFF"> -<H1>Metaprogramming in Python 1.5 (DRAFT)</H1> +<H1>Metaclasses in Python 1.5</H1> +<H2>(A.k.a. The Killer Joke :-)</H2> -<H4>XXX This is very much a work in progress.</H4> - -<P>While Python 1.5 is only out as a <A -HREF="http://grail.cnri.reston.va.us/python/1.5a3/">restricted alpha -release</A>, its metaprogramming feature is worth mentioning. +<P><b>Note: this document describes a feature only released in <A +HREF="../../1.5a3/">Python 1.5a3</A>.</b> <P>In previous Python releases (and still in 1.5), there is something called the ``Don Beaudry hook'', after its inventor and champion. @@ -144,7 +142,7 @@ class C: the class namespace's contents would be {'a': 1, 'f': <function f ...>}. -<P>But enough already about Python metaprogramming in C; read the +<P>But enough already about writing Python metaclasses in C; read the documentation of <A HREF="http://maigret.cog.brown.edu/pyutil/">MESS</A> or <A HREF="http://www.digicool.com/papers/ExtensionClass.html" >Extension @@ -153,7 +151,7 @@ Classes</A> for more information. <H2>Writing Metaclasses in Python</H2> <P>In Python 1.5, the requirement to write a C extension in order to -engage in metaprogramming has been dropped (though you can still do +write metaclasses has been dropped (though you can still do it, of course). In addition to the check ``is the type of the base class callable,'' there's a check ``does the base class have a __class__ attribute.'' If so, it is assumed that the __class__ @@ -189,8 +187,8 @@ new (meta)inststance of the base class's metaclass. <P>Going back to the example, the class B.__class__ is instantiated, passing its constructor the same three arguments that are passed to -the default class constructor or to an extension's metaprogramming -code: <i>name</i>, <i>bases</i>, and <i>namespace</i>. +the default class constructor or to an extension's metaclass: +<i>name</i>, <i>bases</i>, and <i>namespace</i>. <P>It is easy to be confused by what exactly happens when using a metaclass, because we lose the absolute distinction between classes @@ -244,7 +242,7 @@ How did this happen? MySpecialClass is an instance of MetaClass1 __call__ method is invoked, and presumably the __call__ method defined by MetaClass1 returns an instance of HelperClass1. -<P>Now let's see how we could use metaprogramming -- what can we do +<P>Now let's see how we could use metaclasses -- what can we do with metaclasses that we can't easily do without them? Here's one idea: a metaclass could automatically insert trace calls for all method calls. Let's first develop a simplified example, without @@ -424,7 +422,7 @@ doesn't support all these features yet. <H1>Real-life Examples</H1> <P>Have a look at some very preliminary examples that I coded up to -teach myself how to use metaprogramming: +teach myself how to write metaclasses: <DL> |