[Python] Pandas Timedelta in months

How can I calculate the elapsed months using pandas? I have write the following, but this code is not elegant. Could you tell me a better way?

import pandas as pd

df = pd.DataFrame([pd.Timestamp('20161011'),
pd.Timestamp('20161101') ], columns=['date'])
df['today'] = pd.Timestamp('20161202')

df = df.assign(
elapsed_months=(12 *
(df["today"].map(lambda x: x.year) -
df["date"].map(lambda x: x.year)) +
(df["today"].map(lambda x: x.month) -
df["date"].map(lambda x: x.month))))
# Out[34]:
# date today elapsed_months
# 0 2016-10-11 2016-12-02 2
# 1 2016-11-01 2016-12-02 1

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