NameError: name 'tempita' is not defined when building extensions with old cython

[toobaz]

Code Sample, a copy-pastable example if possible

pietro@debiousci:~/nobackup/repo/pandas_temp$ python3 setup.py build_ext --inplace 
Traceback (most recent call last):
  File "setup.py", line 813, in <module>
    ext_modules=maybe_cythonize(extensions, compiler_directives=directives),
  File "setup.py", line 541, in maybe_cythonize
    build_ext.render_templates(_pxifiles)
  File "setup.py", line 127, in render_templates
    pyxcontent = tempita.sub(tmpl)
NameError: name 'tempita' is not defined

Problem description

If cython is too old/missing, the nice error reporting of the setup.py do not work.

Until few minutes ago I had never heard about tempita, but my understanding is that it is required (used in build_ext.render_templates) while cython is not:

pandas/setup.py

Line 74 in bee17d5

cython = False

Hence, whether the check for tempita is made should not depend on whether cython is found: instead, this is what currently happens, given that tempita is checked in the else clause of the try...except check of cython:

pandas/setup.py

Line 76 in bee17d5

try:

Notice that this means the above error pops out despite tempita being installed in my system.

Expected Output

None

Output of pd.show_versions()

Commit: bee17d5

[toobaz]

(By the way: my command above will fail anyway because of the missing cython, but my understanding is that, because of this bug, setup.py will fail even when cython files are provided - and hence cython is not needed)

[jreback]

we bumped cython recently; conda update cython should be enough
this is a dev only dep and only if not creating a new from a new env

if you don’t have cython it actually would work

[toobaz]

Yep, sorry for not mentioning I had already solved my local problem.

[jorisvandenbossche]

I suppose this is caused by #28374 when we now require cython for sdists. Before, we only called cythonize when if cython, but now we assume cython is installed in maybe_cythonize. We can add a check there if cython/tempita is installed and otherwise raise a better error message?

[toobaz]

I think (but I'm quite ignorant of how the setup.py works) that just moving the following try..except

pandas/setup.py

Line 76 in bee17d5

try:

... out of the else should fix this...

[WillAyd]

I think that block could be simplified - the pip install Tempita command I don't believe is valid any longer.

I generally think anything to simplify setup.py would be great. I would be hesitant to add more logic

[jorisvandenbossche]

@toobaz I don't think that should be moved out of the else clause, as in theory you don't need tempita to run setup.py (eg sdist does not need it).

But I think @WillAyd is correct that the import tempita / pip install tempita is no longer needed, it might stem from a time that we still supported cython versions that did not include tempita

[toobaz]

@toobaz I don't think that should be moved out of the else clause, as in theory you don't need tempita to run setup.py (eg sdist does not need it).

Right, it would need also a variable where we remember whether tempita is present, like for cython.

But I think @WillAyd is correct that the import tempita / pip install tempita is no longer needed, it might stem from a time that we still supported cython versions that did not include tempita

Again, I'm not an expert, but my understanding is that if you have tempita but not cython, the setup.py still tried to allow you to take a pandas provided with cython files and compile them to C. But then, this is a very marginal use case, so maybe not worth the effort.

[jorisvandenbossche]

if you have tempita but not cython, the setup.py still tried to allow you to take a pandas provided with cython files and compile them to C

tempita itself is not enough to compile cython file to C (tempita only generates cython files from the templates, not C files), so that use case doesn't sound possible to me.

So I think it should be fine to just rely on tempita provided by cython?

[toobaz]

tempita itself is not enough to compile cython file to C (tempita only generates cython files from the templates, not C files), so that use case doesn't sound possible to me.

OK sorry, now I understand, and sure, checking ``tempita'' is useless.