Expose __pyx_f variable

[Ray Chen]

Hello everyone

I am using cythonize to make .c files from my pure python files. Sometimes the __pyx_f variable isn't the same as the file path so how can i get the value from pure python?

I do not want to modify the .c source code, and the value seems to be used in tracebacks too (for the filename in each frame).

[D Woods]

I don't know why you need it, but this sounds like the wrong solution to your problem. However:

__pyx_f isn't a single filename but an array of filenames - Cython source code can come from a number of places (a pyx file, a pxd file, a file that's been included in another, utility code that Cython itself generates). As far as I can tell __pyx_f is only used for generating tracebacks and thus which element is picked depends on where the traceback comes from. I don't know how or if they are ordered.

You could access it by modifying the source code of your Cython file. I would probably declare it as an extern variable:

cdef extern from *:

    const char* __pyx_f[]

You can then create a Cython function to access the variable:

def get_from_pyx_f(n):

    return __pyx_f[n]

I don't think there's any way of telling how big the array is so this risks a segmentation fault if you try to access too far. None of this is tested so it may need small modifications to work.

Alternatively you could write a function that generates a traceback and then extract the file name from that.

[Stefan Behnel]

Am 26. August 2021 22:54:18 MESZ schrieb Ray Chen:
>I am using cythonize to make .c files from my pure python files.
>Sometimes
>the __pyx_f variable isn't the same as the file path so how can i get
>the value from pure python?

You can use the normal Python variables like "__file__" etc.

Stefan

[Ray Chen]

Oh, is this how you access C variables from Cython? I'll check it out!

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[Stefan Behnel]

Am 27. August 2021 21:26:46 MESZ schrieb D Woods:
> I don't know why you need it, but this sounds like the wrong solution
> to your problem.

Yes.

>would probably declare it as an extern variable:
>
>cdef extern from *:
> const char* __pyx_f[]
>
>You can then create a Cython function to access the variable:
>
>def get_from_pyx_f(n):
> return __pyx_f[n]

Note, though, that anything prefixed with "__pyx_" and friends is internal to Cython and subject to change at any time, without warning. Use at your own risk.

Stefan