python - Odd results from simple group by -

the code below returning information not expecting. issue or missing something?

import pandas pd df = pd.dataframe({'symbol':['a','b','c'],                    'volume':[561,56,8]})  group = df.groupby('symbol')  def f1(group):     print group     return group  group.apply(f1) 

i getting:

  symbol  volume   0          561     symbol  volume   0          561     symbol  volume   1      b      56     symbol  volume   2      c       8   

as can see issue print statement. getting group "a" twice , not sure if bug. can confirm?

pandas version : '0.14.1'

from pandas documentation:

warning: in current implementation apply calls func twice on first group decide whether can take fast or slow code path. can lead unexpected behavior if func has side-effects, take effect twice first group.

that's why method called once on first group. it's by-implementation.