[Cython] unsupported meta-programming-related features

[Xuancong Wang]

Sorry, I have a few extra steps which map all parser symbols into the
global space.

parser = argparse.ArgumentParser(...)
parser.add_argument('-ht', '--headtail', help='add headtail',
default=False, action='store_true')
opt=parser.parse_args()
globals().update(vars(opt))

xuancong

On Wed, Apr 20, 2016 at 1:41 AM, Robert Bradshaw <robertwb at gmail.com> wrote:
> On Tue, Apr 19, 2016 at 2:13 AM, Xuancong Wang <xuancong84 at gmail.com> wrote:
>>
>> Dear Cython developers,
>>
>> Python supports meta-programming, in which a variable with name
>> specified in a string can be created at run-time. One built-in library
>> which make use of this is argparse.
>>
>> For example:
>>
>> parser.add_argument('-N', '--max_threads', help='maximum number of
>> concurrent decoding threads', type=int, default=16)
>>
>> in this case, the variable max_threads is created from the string
>> argument. And then Cython will generate an incorrect C program with
>> the following error:
>>
>> smt.py:78:88: undeclared name not builtin: headtail
>> smt.c:1:2: error: #error Do not use this file, it is the result of a
>> failed Cython compilation.
>
>
> Argparse works just fine in Cython
>
> import argparse
> parser = argparse.ArgumentParser()
> parser.add_argument('-N', '--max_threads', help='maximum number of
> concurrent decoding threads', type=int, default=16)
> args = parser.parse_args()
> print args.max_threads
>
> Could you provide a full example that you think should work? Where is
> headtail defined? Is it another argument?
>
>>
>> In comparison, I found that nuitka can convert this kind of Python
>> programs sucessfully. I hope Cython can be improved. Thanks!
>
>
> argsparse dynamically adds the attributes to the returned object, which
> works fine in Cython. Unless you're doing something like
>
> http://stackoverflow.com/questions/19299635/python-argparse-parse-args-into-global-namespace-or-a-reason-this-is-a-bad-idea
>
> That's one of the few places we diverge, because people strongly preferred
> compile-time errors to runtime errors in this case.
>
>
> _______________________________________________
> cython-devel mailing list
> cython-devel at python.org
> https://mail.python.org/mailman/listinfo/cython-devel
>