# Lower all values
df.columns = [x.lower() for x in df.columns]

# Strip out punctuation, replace spaces and lower
df.columns = df.columns.str.replace("[^\w\s]", "").str.replace(" ", "_").str.lower()

# Condense multiindex columns
df.columns = ["_".join(col).lower() for col in df.columns]

# Double transpose to remove bottom row for multiindex columns
df.T.reset_index(1, drop=True).T