I know pandas is built on NumPy, and my class examples also always include import NumPy first. I'm just not sure if this is a required step or a "just in case" type situation.
It's not necessary to import numpy before importing pandas. For example:
In [1]: import pandas as pd
In [2]: s = pd.Series(range(10))
In [3]: s
Out[3]:
0 0
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
dtype: int64
The reason that it is often imported along with pandas is that you often will create an array using numpy which is then passed to pandas.