When you pass a string to exec
or eval
, it compiles that string to a code object before considering globals or locals. So when you say:
eval('lambda: a', ...)
it means:
eval(compile('lambda: a', '<stdin>', 'eval'), ...)
There's no way for compile
to know that a
is a freevar, so it compiles it to a global reference:
>>> c= compile('lambda: a', '<stdin>', 'eval')
>>> c.co_consts[0]
<code object <lambda> at 0x7f36577330a8, file "<stdin>", line 1>
>>> dis.dis(c.co_consts[0])
1 0 LOAD_GLOBAL 0 (a)
3 RETURN_VALUE
Therefore to make it work you have to put a
in the globals and not the locals.
Yeah, it's a bit dodgy. But then that's exec
and eval
for you I suppose... they're not supposed to be nice.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…