pandas (original) (raw)

I think there might be an issue with reindex(..., takeable=True) introduced in a recent release and you might want to consider deprecating/dropping it while it hasn't crept to user code too much.

The main reason is that reindex takeable is conceptually different from reindex: the latter can introduce new rows with values that must be filled while the former cannot. Essentially, reindex takeable is no more than a fancy indexing operation of numpy which is already available via iloc indexer. If you consider reindex parameters, you can see there' no additional value in reindex takeable:

method, limit & fill_value parameters are useless since no empty cells can appear
level parameter should be available to user via fancy multiindex slicing added recently
copy is also achievable via .copy() method

So not only it adds no value, but it also increases complexity:

externally, by adding yet another way to do fancy indexing
internally, by adding more code paths to follow when implementing & executing reindex

The last point has already caused a bug:

In [1]: s = pd.Series(list('abc'), index=np.arange(3)[::-1])

In [2]: s Out[2]: 2 a 1 b 0 c dtype: object

In [3]: s.take([2,1,0]) Out[3]: 0 c 1 b 2 a dtype: object

In [4]: s.reindex([2,1,0], takeable=True) Out[4]: 2 a 1 b 0 c dtype: object

In [5]: s.iloc[[2,1,0]] Out[5]: 2 a 1 b 0 c dtype: object

Of course, this can be fixed by inserting workarounds here and here but this will increase complexity even more and won't address the conceptual issue.