gfonts-2-filter-func.py

import re

def filter_fonts(df, regex_filters):
    df_new = pd.concat([df.filter(regex=re.compile(regex, re.IGNORECASE), axis=1).sum(axis=1).astype(bool) for regex in regex_filters], axis=1)
    mask = df_new.all(axis=1)
    return list(df.loc[mask].family)

filtered_fontnames = filter_fonts(df, ['Black', 'cyrillic', '_serif'])
filtered_fontnames