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Signature error with exceptval #1913

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jbrockmendel opened this Issue Oct 5, 2017 · 5 comments

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jbrockmendel commented Oct 5, 2017

Just upgraded to 0.27.1, psyched to try out @cython.exceptval. Tried it out on pandas._libs.tslib._Timestamp._compare_outside_nanorange:

Existing:

    cdef bint _compare_outside_nanorange(_Timestamp self, datetime other,
                                         int op) except -1:

New:

    @cython.exceptval(-1)
    @cython.locals(self=_Timestamp, other=datetime, op=int)
    @cython.returns(cython.bint)
    @cython.cfunc
    def _compare_outside_nanorange(self, other, op):

build_ext complained that _compare_outside_nanorange is not declared in the pxd file, so I added it:

cdef class _Timestamp(datetime):
    cdef bint _compare_outside_nanorange(_Timestamp self, datetime other, int op) except -1

build_ext now produces the error message Signature not compatible with previous declaration. AFAICT the signatures should be compatible; am I missing something?

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jbrockmendel Oct 6, 2017

Since you have a .pxd, you don't need the Decorators at all. Well, not in a .py file, at least. Not sure about .pyx.

This is in a pyx. The pxd file contains only the small subset of functions exported. In fact, under the status quo, the _Timestamp class doesn't exist in the pxd at all.

There's no use in typing "self" since its type is obvious.

Makes sense, thanks.

@cython.locals() does not change the signature. That's a known limitation, can't look up the ticket right now.

I'm not sure what to make of this. Elsewhere I've been using (in .pyx files)

@cython.locals(foo=bar)
@cython.cfunc
def somefunc(foo):
    [...]

interchangeably with

cdef somefunc(bar foo):
    [...]

In some of these cases I haven't bothered putting somefunc in the accompanying pxd file, in others it would just be cdef somefunc(bar foo). Have I been using this incorrectly?

jbrockmendel commented Oct 6, 2017

Since you have a .pxd, you don't need the Decorators at all. Well, not in a .py file, at least. Not sure about .pyx.

This is in a pyx. The pxd file contains only the small subset of functions exported. In fact, under the status quo, the _Timestamp class doesn't exist in the pxd at all.

There's no use in typing "self" since its type is obvious.

Makes sense, thanks.

@cython.locals() does not change the signature. That's a known limitation, can't look up the ticket right now.

I'm not sure what to make of this. Elsewhere I've been using (in .pyx files)

@cython.locals(foo=bar)
@cython.cfunc
def somefunc(foo):
    [...]

interchangeably with

cdef somefunc(bar foo):
    [...]

In some of these cases I haven't bothered putting somefunc in the accompanying pxd file, in others it would just be cdef somefunc(bar foo). Have I been using this incorrectly?

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May I ask why you seem to prefer the rather verbose decorator syntax over the (IMHO) much more concise dedicated Cython syntax in .pyx files?

If I were to start using a more Python-compatible syntax in .pyx files, I'd certainly prefer the PEP-484 syntax over @locals() and @returns().

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scoder commented Oct 7, 2017

May I ask why you seem to prefer the rather verbose decorator syntax over the (IMHO) much more concise dedicated Cython syntax in .pyx files?

If I were to start using a more Python-compatible syntax in .pyx files, I'd certainly prefer the PEP-484 syntax over @locals() and @returns().

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jbrockmendel Oct 7, 2017

A big part of it at this point is just trying to understand what's going on.

Until very recently I was having no luck getting coverage working in non-trivial cython code, so the main motivation was getting pure-python compatibility in order to get coverage statistics. (other tooling e.g. flake8 was/is part of the motivation, but a much lower priority).

I'd certainly prefer the PEP-484

I'm largely working on pandas and statsmodels, which still support py2.

jbrockmendel commented Oct 7, 2017

A big part of it at this point is just trying to understand what's going on.

Until very recently I was having no luck getting coverage working in non-trivial cython code, so the main motivation was getting pure-python compatibility in order to get coverage statistics. (other tooling e.g. flake8 was/is part of the motivation, but a much lower priority).

I'd certainly prefer the PEP-484

I'm largely working on pandas and statsmodels, which still support py2.

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"I'd certainly prefer the PEP-484 syntax"
I'm largely working on pandas and statsmodels, which still support py2.

Question is, do they have to support it uncompiled? If it's enough to serve Py2 with Cython compiled modules, you can happily use Py3 syntax in them (and compile them with language_level=3).

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scoder commented Oct 7, 2017

"I'd certainly prefer the PEP-484 syntax"
I'm largely working on pandas and statsmodels, which still support py2.

Question is, do they have to support it uncompiled? If it's enough to serve Py2 with Cython compiled modules, you can happily use Py3 syntax in them (and compile them with language_level=3).

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