Pandas Intermediate Cheatsheet

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Pandas Intermediate Cheatsheet

This issue will contains my snippet for pandas that may not be covered in most beginner tutorial and appear quite often in my day to day tasks.

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Reverse One Hot Encoding from get_dummies

Main resource from SO

df_dummies.idxmax(1)

or in more general way, we could create factory like this

def reverse_dummies_factory(pat:str):
    return lambda df_: df_.filter(regex=pat).idxmax(1).str.replace(pat, "")

df_dummies.assign(doc = reverse_dummies_factory("DOC__"))

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Drop certain column based on regex

Main resource from SO (I forgot which questions)

df_.drop(df_.filter(regex='<pattern>').columns, axis=1)

or using pipe and factory function

def drop_columns_factory(colpat:str):
    return lambda df_: df_.drop(df_.filter(regex=colpat).columns, axis=1)

df.pipe(drop_columns_factory(r"<pattern>")

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Pandas Groupby Mechanism

It seems like there's pattern to applying custom aggregation function to a DataFrameGroup in Pandas. The pattern is split-apply-combine. It works like this

TODO: Fill in this implementation details and example