pandas df Extracting number from string before a specific letter code example

Example 1: pandas show column with regular expression

S=pd.Series(['Finland','Colombia','Florida','Japan','Puerto Rico','Russia','france'])
S.str.contains('^F.*')

Example 2: pandas show column with regular expression

S=pd.Series(['Finland','Colombia','Florida','Japan','Puerto Rico','Russia','france'])
[itm[0] for itm in S.str.findall('^[Ff].*') if len(itm)>0]