It`s a private method, but it will do the trick: source._get_numeric_data()
In [2]: import pandas as pd
In [3]: source = pd.DataFrame({'A': ['foo', 'bar'], 'B': [1, 2], 'C': [(1,2), (3,4)]})
In [4]: source
Out[4]:
A B C
0 foo 1 (1, 2)
1 bar 2 (3, 4)
In [5]: source._get_numeric_data()
Out[5]:
B
0 1
1 2