How to iterate over pandas multiindex dataframe using index

One easy way would be to groupby the first level of the index - iterating over the groupby object will return the group keys and a subframe containing each group.

In [136]: for date, new_df in df.groupby(level=0):
     ...:     print(new_df)
     ...:     
                    observation1  observation2
date       Time                               
2012-11-02 9:15:00     79.373668           224
           9:16:00    130.841316           477

                    observation1  observation2
date       Time                               
2012-11-03 9:15:00     45.312814           835
           9:16:00    123.776946           623
           9:17:00    153.766460           624
           9:18:00    463.276946           626
           9:19:00    663.176934           622
           9:20:00    763.773330           621

                    observation1  observation2
date       Time                               
2012-11-04 9:15:00    115.449437           122
           9:16:00    123.776946           555
           9:17:00    153.766460           344
           9:18:00    463.276946           212

What about this?

for idate in df.index.get_level_values('date'):
    complex_process(df.ix[idate], idate)