col_map = pd.Series(df.col1.values,index=df.col2).to_dict()
df['col1'] = df['col2'].map(col_map)
df['d'] = df.apply(lambda x: some_func(a = x['a'], b = x['b'], c = x['c']), axis=1)
def map_many(iterable, function, *other):
if other:
return map_many(map(function, iterable), *other)
return map(function, iterable)