Pandas V0.20 Returns Notimplemented When Multiplying Dataframe Columns

In attempt to answer another question I've been playing around with column-wise multiplication operations in pandas. A = pd.DataFrame({'Col1' : [1, 2, 3], 'Col2' : [2, 3, 4]}) B =

Solution 1:

You can just do:

A.apply(B.Col1.__mul__,0)

Which returns what you're after.

The difference is that B.Col1.values.__mul__ is calling the numpy slot function, but B.Col1.__mul__ is calling a pandas method.

Likely the pandas method was written to avoid some low level headache from numpy:

>>>print(inspect.getsource(pd.Series.__mul__))

def wrapper(left, right, name=name, na_op=na_op):

    if isinstance(right, pd.DataFrame):
        return NotImplemented

    left, right= _align_method_SERIES(left, right)

    converted = _Op.get_op(left, right, name, na_op)

    left, right= converted.left, converted.right
    lvalues, rvalues = converted.lvalues, converted.rvalues
    dtype = converted.dtype
    wrap_results = converted.wrap_results
    na_op = converted.na_op

    if isinstance(rvalues, ABCSeries):
        name = _maybe_match_name(left, rvalues)
        lvalues = getattr(lvalues, 'values', lvalues)
        rvalues = getattr(rvalues, 'values', rvalues)
        # _Op aligns leftandrightelse:
        name = left.name
        if (hasattr(lvalues, 'values') andnot isinstance(lvalues, pd.DatetimeIndex)):
            lvalues = lvalues.values

    result= wrap_results(safe_na_op(lvalues, rvalues))
    return construct_result(
        left,
        result,
        index=left.index,
        name=name,
        dtype=dtype,
    )

Can't find source on the np slot function, but it's likely something similar to this