Pandas: how to extract letters (alpha) from string cell value

Question

I am working on a csv file that contains a lot of location data (addresses) and I want to acquire the street name information without the house number.

A sample of the data:

pd.DataFrame({'OWNERADDR': ['6612 HOLLY RD', '7618 DRESHER RD', '9062 STEINSVILLE '],
             'STREETADDR': ['7713 DRESHER RD', '7606 DRESHER RD', '9072 STEINSVILLE RD']})

What I want is:

Both columns are of str type. But I just want to get rid of the numeric part.

I think there must be a concise way to do it with regular expression. But my lack of knowledge of RE has prevented me from doing so.

Thanks.