re

The re module provides regular expression matching.

Source:

import re

actor main(env):
    m = re.match(r"(foo[a-z]+)", "bla bla foobar abc123")
    if m is not None:
        print("Got a match:", m.group[1])

    env.exit(0)

re.match also accepts an optional start_pos to begin scanning at a specific index (defaults to 0).

Output:

Got a match: foobar

Compiling a pattern once

re.match compiles its pattern on every call. To match the same pattern many times, compile it once with re.compile and use the methods of the Pattern it returns. match, matches and split take the same arguments as the module functions, without the pattern.

Source:

import re

actor main(env):
    ipv4 = re.compile(r"^([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$")
    for address in ["192.168.1.1", "fe80::1", "10.0.0.255"]:
        m = ipv4.match(address)
        if m is not None:
            print(address, "has last octet", m.group[4])
        else:
            print(address, "is not an IPv4 address")

    env.exit(0)

A Pattern does not change after it is created, so actors can share one.

Output:

192.168.1.1 has last octet 1
fe80::1 is not an IPv4 address
10.0.0.255 has last octet 255