pythonpandas

Pandas : make future.no_silent_downcasting working

Python 3.11, Pandas 2.2.3

I currently track FutureWarnings to sanitize an existing code. To silent and opt-in future Downcasting behavior in 'replace' is deprecated and will be removed in a future version, I use pd.set_option("future.no_silent_downcasting", True).

Then, I block on the following minimal example:

import pandas as pd
print(f"{pd.__version__=}")  # '2.2.3'
# discard "Downcasting behavior in `replace`..."
pd.set_option("future.no_silent_downcasting", True)

# Raise en Exception on any Warning:
from warnings import warn, simplefilter
simplefilter('error')  # raise on Warning

df0 = pd.DataFrame({"a": [True, True, False, True, False]})
df1 = pd.DataFrame({"a": [False, True]}, index=[2,4])

# First attempt:
# raise `FutureWarning: Setting an item of incompatible dtype is deprecated and will raise 
# in a future error of pandas. 
# Value '[True True False True True]' has dtype incompatible with bool, please explicitly cast to a compatible dtype first.`
df0.update(df1)  # Raise a FutureWarning

# Second attempt
df0.update(df1.astype(df0.dtypes)) # Also raise the same FutureWarning

I'm a bit confused... How to solve this Warning?

Solution

  • use combine_first

    df0 = df1.combine_first(df0)