Hi,
> I was primarily talking about language support. For quite some time,
> the compiler package wasn't able to compile the Python standard library,
> until Guido van Rossum (and others) brought it back to work at the last
> PyCon. It would simply reject certain more recent language constructs.
> In the process of fixing it, it was also found to deviate from the
> normal language definition, i.e. it would generate bad code.
>
> Many of these are fixed, but it wouldn't surprise me if there are
> still bugs remaining.
I don't know if it can hide some bugs or if the module has just never
been updated to support this bytecode but LIST_APPEND is never emitted.
In the module compiler, list comprehensions are implemented without
emitting this bytecode, howewer the current implementation seems to be
correct from syntax and execution point of view.
For example:
>>> src = "[a for a in range(3)]"
>>> co = compiler.compile(src, 'lc1', 'exec')
>>> co
<code object <module> at 0x404927b8, file "lc1", line 1>
>>> dis.dis(co)
1 0 BUILD_LIST 0
3 DUP_TOP
4 LOAD_ATTR 0 (append)
7 STORE_NAME 1 ($append0)
10 LOAD_NAME 2 (range)
13 LOAD_CONST 1 (3)
16 CALL_FUNCTION 1
19 GET_ITER
>> 20 FOR_ITER 16 (to 39)
23 STORE_NAME 3 (a)
26 LOAD_NAME 1 ($append0)
29 LOAD_NAME 3 (a)
32 CALL_FUNCTION 1
35 POP_TOP
36 JUMP_ABSOLUTE 20
>> 39 DELETE_NAME 1 ($append0)
42 POP_TOP
43 LOAD_CONST 0 (None)
46 RETURN_VALUE
>>> co2 = compile(src, 'lc2', 'exec')
>>> co2
<code object <module> at 0x40492770, file "lc2", line 1>
>>> dis.dis(co2)
1 0 BUILD_LIST 0
3 DUP_TOP
4 STORE_NAME 0 (_[1])
7 LOAD_NAME 1 (range)
10 LOAD_CONST 0 (3)
13 CALL_FUNCTION 1
16 GET_ITER
>> 17 FOR_ITER 13 (to 33)
20 STORE_NAME 2 (a)
23 LOAD_NAME 0 (_[1])
26 LOAD_NAME 2 (a)
29 LIST_APPEND
30 JUMP_ABSOLUTE 17
>> 33 DELETE_NAME 0 (_[1])
36 POP_TOP
37 LOAD_CONST 1 (None)
40 RETURN_VALUE
Cordially,
sébastien martini
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