Pandasで各行に任意の関数を適用するサンプル。遅いらしい:-)

pandas_apply_udf_sample.py

In [1]: import pandas as pd

In [2]: data = {'a': [0,1,2], 'b': [3,4,5]}
   ...: df = pd.DataFrame(data)
   ...: df
   ...: 
Out[2]: 
   a  b
0  0  3
1  1  4
2  2  5

In [3]: def f(r):
   ...:     return '{:d} + {:d} = {:d}'.format(r['a'], r['b'], r['a'] + r['b'])
   ...: 

In [4]: df['c'] = df.apply(f, axis=1)
   ...: df
   ...: 
Out[4]: 
   a  b          c
0  0  3  0 + 3 = 3
1  1  4  1 + 4 = 5
2  2  5  2 + 5 = 7