ENH: ndarray.isin

[MaxGhenis]

Proposed new feature or change:

numpy.isin is equivalent to pandas.{Series,DataFrame}.isin. Adding numpy.ndarray.isin would produce consistency with pandas and save 4 characters:

np.isin(x, y)  # Current
x.isin(y)      # Proposed

I've posted this idea to the forum here.

[adeak]

There are plenty of numpy functions that aren't ndarray methods but are pandas.Series methods:

>>> import numpy as np
>>> import pandas as pd
>>> series_methods = [attr for attr in dir(pd.Series) if callable(getattr(pd.Series, attr))]
>>> array_methods = [attr for attr in dir(np.ndarray) if callable(getattr(np.ndarray, attr))]
>>> setdiff = set(series_methods) - set(array_methods)
>>> [attr for attr in dir(np) if attr in setdiff]
['__getattr__', 'abs', 'add', 'append', 'cov', 'diff', 'divide', 'divmod', 'isin', 'median', 'mod', 'multiply', 'pad', 'product', 'quantile', 'subtract', 'unique', 'where']

Numpy devs are usually very reluctant to inflate the ndarray namespace. And there are a lot of more commonly useful methods in that list, for instance np.diff.