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
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