how to do a left,right and mid of a string in a pandas dataframe

First two letters for each value in a column:

>>> df['StateInitial'] = df['state'].str[:2]
>>> df
   pop       state  year StateInitial
0  1.5    Auckland  2000           Au
1  1.7       Otago  2001           Ot
2  3.6  Wellington  2002           We
3  2.4     Dunedin  2001           Du
4  2.9    Hamilton  2002           Ha

For last two that would be df['state'].str[-2:]. Don't know what exactly you want for middle, but you can apply arbitrary function to a column with apply method:

>>> df['state'].apply(lambda x: x[len(x)/2-1:len(x)/2+1])
0    kl
1    ta
2    in
3    ne
4    il

With regards to the mid, probably a short cut code would be df['state'].str[3,5]

this will start from the 3rd character and give you the 3rd and 4th character of the string.