substring function to create new column

[scidam]

I would solve the problem as follows:

import pandas as pd
data = {'id': ['aa11bc', 'bb22cd', 'cc33ef', 'dd44gh', 'ee55ij','ff66kl','gg77mn','hh88op'], 
        'direction': ["north, south, east, west", "north, south, east, west", "north, south, east, west", "north, south, east, west",
                      "north, south, east, west","north, south, east, west","north, south, east, west"
                     ,"north, south, east, west"]}
df = pd.DataFrame(data, columns = ['id','direction'])

def get_direction(row):
    mapper = {'%s%s' % (a, n): k // 2 for k, (a, n) in enumerate(zip('abcdefgh', '12345678'))}
    index = mapper.get(row['id'][1:3].lower())
    if index is not None:
        return row['direction'].split(',')[index]

df['position'] = df.apply(get_direction, axis=1)

However, direction column doesn't change, this probably can be used to get completely vectorized solution of the problem,
which would be faster.