>> This might be minor-- but I didn't see anyone mentioning it so far.
>> If `exec` functionality is to be provided, then I think it still
>> should be a keyword for the parser to know; currently bytecode
>> generation is affected if `exec` is present. Even if that changes
>> for Python 3k (we don't know yet), the paragraph for exec should be
>> annotated with a note about this issue.
Brett> But the PEP says that 'exec' will become a function and thus no
Brett> longer become a built-in, so changing the grammar is not needed.
I don't think that was the OP's point though it might not have been terribly
clear. Today, the presence of the exec statement in a function changes how
non-local load instructions are generated. Consider f and g with their
dis.dis output:
>>> def f(a):
... exec "import %s" % a
... print q
...
>>> def g(a):
... __import__(a)
... print q
...
>>> dis.dis(f)
2 0 LOAD_CONST 1 ('import %s')
3 LOAD_FAST 0 (a)
6 BINARY_MODULO
7 LOAD_CONST 0 (None)
10 DUP_TOP
11 EXEC_STMT
3 12 LOAD_NAME 1 (q)
15 PRINT_ITEM
16 PRINT_NEWLINE
17 LOAD_CONST 0 (None)
20 RETURN_VALUE
>>> dis.dis(g)
2 0 LOAD_GLOBAL 0 (__import__)
3 LOAD_FAST 0 (a)
6 CALL_FUNCTION 1
9 POP_TOP
3 10 LOAD_GLOBAL 2 (q)
13 PRINT_ITEM
14 PRINT_NEWLINE
15 LOAD_CONST 0 (None)
18 RETURN_VALUE
If the exec statement is replaced by a function, how will the bytecode
generator know that q should be looked up using LOAD_NAME instead of
LOAD_GLOBAL? Maybe it's a non-issue, but even if so, a note to that affect
on the wiki page might be worthwhile.
Skip
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