Preserve stack trace when a curried function fails

[jni]

I'm not sure how difficult this is or how it would affect performance, but it sure as hell would be more fun to debug things!

Current stack trace:

883     >>> montaged = list(montage_stream(images, [[0, 1], [2, 3]], [2, 0, 1]))
UNEXPECTED EXCEPTION: TypeError()
Traceback (most recent call last):

  File "/Users/nuneziglesiasj/anaconda/envs/mic3/lib/python3.4/doctest.py", line 1318, in __run
    compileflags, 1), test.globs)

  File "<doctest microscopium.preprocess.montage_stream[1]>", line 1, in <module>

  File "/Volumes/Projects/microscopium/microscopium/preprocess.py", line 903, in montage_stream
    curried.map(stack_channels(channel_order)),

  File "cytoolz/functoolz.pyx", line 252, in cytoolz.functoolz.curry.__call__ (cytoolz/functoolz.c:3296)

TypeError

/Volumes/Projects/microscopium/microscopium/preprocess.py:883: UnexpectedException

The actual error, after some sleuthing around in IPython:

----> 1 def is_array(obj): return isinstance(obj, np.array)

TypeError: isinstance() arg 2 must be a type or tuple of types

[eriknw]

I agree this would be nice. I don't know whether this is possible or not, but we can look into it.

[mrocklin]

When looking into profiling cython code I learned that there was a flag you could set. That's an option.

Alternatively @jni you could use toolz.curry if performance isn't that big of an issue.

We could also capture the exception, capture the traceback, and then raise a new exception with that printed out traceback. This is what I do in dask. It's a bit of a pain to do. Contributions welcome :)

[jni]

@mrocklin it won't happen immediately but I'll post here if I grab some time to start on this.

Slightly related: have you guys measured the performance hit of currying functions? i.e. why not curry all the things?

[mrocklin]

Erik benchmarked this extensively.

We did curry all the things. Have you seen the toolz.curried namespace?

[jni]

@mrocklin yes, but why is that not the default namespace. ;)