DataFrame gives uninformative error message when comparing to constants

[hammer]

For any DataFrame with numeric values, saying something like df == 'cmp'results in PandasError: DataFrame constructor not properly called!, which is pretty unintuitive. I'm not sure what behavior would be correct, but I do know that this error message is not helpful.

[wesm]

Surprised this never came up until now:

In [9]: np.random.randn(10) == 'cmp'
Out[9]: False

Easy to check for and will raise a more helpful exception