On Thu, 01 Jul 2010 11:55:05 +0200, Thomas Jollans wrote:
> On 07/01/2010 11:12 AM, moerchendiser2k3 wrote:
>> Hi all,
>>
>> when I have a PyCodeObject, is there any way to extract a doc string
>> from the code?
>> For instance the following script
>
> Code objects don't have doc strings, as such. However, for functions at
> least (this may or may not be true for code originating elsewhere), it
> appears that the code's first constant is always the docstring, even if
> it's None:
Nope, you're misinterpreting what you're seeing. Here's a counter-example
from Python 3.1:
>>> def f():
... 999
... return 42
...
>>> f.__code__.co_consts
(None, 42)
The docstring is None, unless the function definition is immediately
followed by a string literal, in which case the string literal is taken
as the docstring. Any other object is removed by the keyhole optimizer:
>>> import dis
>>> dis.dis(f)
3 0 LOAD_CONST 1 (42)
3 RETURN_VALUE
In older versions of Python, the keyhole optimizer was less clever.
Here's an example from 2.4:
>>> def f():
... 999
... return 42
...
>>> f.func_code.co_consts
(None, 999, 42)
>>> import dis
>>> dis.dis(f)
2 0 LOAD_CONST 1 (999)
3 POP_TOP
3 4 LOAD_CONST 2 (42)
7 RETURN_VALUE
Aside: Python's keyhole optimizer has removed unreachable string
constants (other than doc strings) at least since Python 1.5. But doing
the same to other object types had to wait until Python 2.5.
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
