[Python-Dev] doc behavior in class definitions

Sat Oct 8 00:51:21 CEST 2005

Martin,
These two cases generate different bytecode.
 def foo(): # foo.func_code.co_flags == 0x43
 print x # LOAD_FAST 0
 x = 3
 class Foo: # <code object>.co_flags == 0x40
 print x # LOAD_NAME 'x'
 x = 3
In functions, local variables are just numbered slots. (co_flags bits
1 and 2 indicate this.) The LOAD_FAST opcode is used. If the slot is
empty, LOAD_FAST throws.
In other code, the local variables are actually stored in a
dictionary. LOAD_NAME is used. This does a locals dictionary lookup;
failing that, it falls back on the globals dictionary; and failing
that, it falls back on builtins.
Why the discrepancy? Beats me. I would definitely implement what
CPython does up to this point, if that's your question.
Btw, functions that use 'exec' are in their own category way out
there:
 def foo2(): # foo2.func_code.co_flags == 0x42
 print x # LOAD_NAME 'x'
 exec "x=3" # don't ever do this, it screws everything up
 print x
Pretty weird. Jython seems to implement this.
-j

[Python-Dev] __doc__ behavior in class definitions

[Python-Dev] doc behavior in class definitions