>>> import pandas as pd >>> import numpy as np >>> s = pd.Series(["a","b","c","a", np.nan], dtype="category") >>> s 0 a 1 b 2 c 3 a 4 NaN dtype: category Categories (3, object): [a, b, c] # `na=False` kwarg should make all missing values False, but this seems broken for categoricals  >>> s.str.contains("a", na=False) 0 True 1 False 2 False 3 True 4 NaN dtype: object # compare that to object series >>> s2 = pd.Series(["a","b","c","a", np.nan]) >>> s2 0 a 1 b 2 c 3 a 4 NaN dtype: object >>> s2.str.contains("a", na=False) 0 True 1 False 2 False 3 True 4 False dtype: bool

>>> s = pd.Series(["a","b","c","a", np.nan], dtype="category") >>> s2 = pd.Series(["a","b","c","a", np.nan]) >>> (s.str.contains("a", na=False) == s2.str.contains("a", na=False)).all() True