[Python-Dev] defmacro (was: Anonymous blocks)
jimjjewett at gmail.com
Fri Apr 22 23:36:19 CEST 2005
As best I can tell, the anonymous blocks are used to take
care of boilerplate code without changing the scope -- exactly
what macros are used for. The only difference I see is that in
this case, the macros are limited to entire (possibly compound)
To make this more concrete,
>> in synchronized(the_lock):
> s/in/with/ to get PEP 310.
>Guido's recent screed crystallised the idea of writing resources
> as two-part generators:
[Adding Reinhold Birkenfeld's suggestion of a blank yield]
> def my_resource():
> print "Hi!" # Do entrance code
> yield # Go on with the contents of the 'with' block
> print "Bye!" # Do exit code
The macro itself looks reasonable -- so long as there is only
ever one changing block inside the macro. I'm not sure that
is a reasonable restriction, but the alternative is ugly enough
that maybe passing around locals() starts to be just as good.
What about a block that indicates the enclosed namespaces
will collapse a level?
<make explicit calls to named callback "functions", but
within the same locals() scope.>
Then myresource, reader, writer, and fn would share a
namespace without having to manually pass it around.
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