==== groups, random integers, and random floats ====
<code>
In [6]: 
import pandas as pd
import numpy as np
rand = np.random.RandomState(1)
df = pd.DataFrame({'A': ['foo', 'bar'] * 3,
                   'B': rand.randn(6),
                   'C': rand.randint(0, 20, 6)})

In [7]: 
print(df)
     A         B   C
0  foo  1.624345   5
1  bar -0.611756  18
2  foo -0.528172  11
3  bar -1.072969  10
4  foo  0.865408  14
5  bar -2.301539  18
</code>

Useful for things like
<code>
In [8]: 
gb = df.groupby(['A'])
</code>

Ref:
  * Found it in https://stackoverflow.com/questions/14734533/how-to-access-subdataframes-of-pandas-groupby-by-key