pandas Python Series objects are mutable, thus they cannot be hashed in query method

Question

I'm tring to run:

import pandas as pd
df_data = pd.DataFrame({'a':[1,20,None,40,50]})
df_data.query('a.isnull()')

and an error happens :

TypeError: 'Series' objects are mutable, thus they cannot be hashed

but:

df_data.a.isnull()

has no error at all, why is this happening? can you help me to figure out why?

Answer 1

Use python engine, or use a np.array with the default npexpr engine.

df_data.query('a.isnull()', engine='python')

or

df_data.query('a.isnull().values')

(Not quite sure why numexpr can't handle a pd.Series though)