s = re.search('\\d+(\\.\\d+)?', I)
s.group(0)
I = 'A=3V'
s = re.search('\\d+(\\.\\d+)?', I)
s.group(0)
I = 'I=2.723A'
s = re.search('\\d+(\\.\\d+)?', I)
s.group(0)
Extracting a number from a 1-word string