Since most of the answers use ifconfig to extract the IPv4 from the eth0 interface, which is deprecated in favor of ip addr, the following code could be used instead:
import os
ipv4 = os.popen('ip addr show eth0 | grep "\<inet\>" | awk \'{ print $2 }\' | awk -F "/" \'{ print $1 }\'').read().strip()
ipv6 = os.popen('ip addr show eth0 | grep "\<inet6\>" | awk \'{ print $2 }\' | awk -F "/" \'{ print $1 }\'').read().strip()
Alternatively, you can shift part of the parsing task to the python interpreter by using split() instead of grep and awk, as @serg points out in the comment:
import os
ipv4 = os.popen('ip addr show eth0').read().split("inet ")[1].split("/")[0]
ipv6 = os.popen('ip addr show eth0').read().split("inet6 ")[1].split("/")[0]
But in this case you have to check the bounds of the array returned by each split() call.
Another version using regex:
import os
import re
ipv4 = re.search(re.compile(r'(?<=inet )(.*)(?=\/)', re.M), os.popen('ip addr show eth0').read()).groups()[0]
ipv6 = re.search(re.compile(r'(?<=inet6 )(.*)(?=\/)', re.M), os.popen('ip addr show eth0').read()).groups()[0]