python error TypeError:Cannot convert the series to class float

import pandas as pd
Series=pd.Series(["$3.9","$1.6","abc","bc","bb","c"])
# Take the number float and replace Na with a float type
print Series.str.extract("([1-9]\d*\. \d*|0\. \d*[1-9]\d*)",expand=True).fillna(value=0).astype(float)

 float(seriers)がなく、astype()のみでfloatにする。