The apply method over a group seems to visit the first group twice
It seems that the apply method of a group invokes the function passed as parameter once for each group, as expectes. However, the function is invoked twice for the first group. Enclose is a short code reproducing this behavior. Is it a normal behavior or am I doing something wrong here.

I run the code with pandas 0.10.0 on. Windows 7, 32 bit version.

The code reproducing this  behavior:

import pandas as pd

tdf      = pd.DataFrame( { 'cat' : [1,1,1,2,2,1,1,2], 'B' : range(8)})
category = tdf['cat']
pGroups = tdf.groupby(by=category)

def getLen(df) :
    print  'len ',len(df)
    return len(df)

plen = pGroups.apply(getLen)
