import re

text = "Isaac Newton, fyzik"

m = re.match(r'(\w+) (\w+)', text)

print(m.group(0))
print(m.group(1))
print(m.group(2))
print(m.groups())

print(re.sub(r'(\w+) (\w+)', r'\2, \1', text))

print(re.sub(r'(\d+). (\d+). (\d+)', r'\3-\2-\1', "20. 11. 2017"))