<[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
| >From the manual:
|
| "code objects are immutable and contain no references (directly or
| indirectly) to mutable objects" (3.2)
|
| I thought my code worked with both mutable and immutable objects.
| Whassup?
Consider the following:
>>> def g(): return (1,2), [1,2]
>>> dis.dis(g)
1 0 LOAD_CONST 3 ((1, 2))
3 LOAD_CONST 1 (1)
6 LOAD_CONST 2 (2)
9 BUILD_LIST 2
12 BUILD_TUPLE 2
15 RETURN_VALUE
>>> g.func_code.co_consts
(None, 1, 2, (1, 2))
The code object stores the immutables 1, 2, and (1,2) but not the mutable
[1,2]. Rather it stores immutable code to create the mutable list.
I tried to see if the addition of closures violated the stipulation, using
>>> def f():
l = []
def _(x):
l.append(x)
return _
but the inner code object only knows the list by the (immutable) name 'l',
which does not count as a reference. Such code objects cannot be directly
exec'ed but only executed indirectly by calling the function that wraps it
and that has the reference to the in-this-case mutable object. (The
mapping from 'l' to that object appears to be hidden.)
Terry Jan Reedy
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