Numpy isnan() fails on an array of floats (from pandas dataframe apply)

Question

I have an array of floats (some normal numbers, some nans) that is coming out of an apply on a pandas dataframe.

For some reason, numpy.isnan is failing on this arra

Answer 1

On top of @unutbu answer, you could coerce pandas numpy object array to native (float64) type, something along the line

import pandas as pd
pd.to_numeric(df['tester'], errors='coerce')

Specify errors='coerce' to force strings that can't be parsed to a numeric value to become NaN. Column type would be dtype: float64, and then isnan check should work