You can use BDay() to get the business days in range. For example -
from pandas.tseries.offsets import *
In [185]: s
Out[185]:
2011-01-01 -0.011629
2011-01-02 -0.089666
2011-01-03 -1.314430
2011-01-04 -1.867307
2011-01-05 0.779609
2011-01-06 0.588950
2011-01-07 -2.505803
2011-01-08 0.800262
2011-01-09 0.376406
2011-01-10 -0.469988
Freq: D
In [186]: s.asfreq(BDay())
Out[186]:
2011-01-03 -1.314430
2011-01-04 -1.867307
2011-01-05 0.779609
2011-01-06 0.588950
2011-01-07 -2.505803
2011-01-10 -0.469988
Freq: B