Exercise 1 solution

    import re
    text = "Smith, Ann: 2026-11-02\nJones, Bo: 2025-01-09"

    out = re.sub(r"^(?P<last>\w+), (?P<first>\w+): (?P<y>\d{4})-(?P<m>\d\d)-(?P<d>\d\d)$",
                 r"\g<first> \g<last>: \g<d>/\g<m>/\g<y>", text, flags=re.M)
    print(out)
    # Ann Smith: 02/11/2026
    # Bo Jones: 09/01/2025

    print(re.subn(r"^(\w+), (\w+)", r"\2 \1", text, flags=re.M)[1])
    # 2

(All lines were run and printed exactly what is shown.)

Explanation: re.M lets ^ and $ work on every line, so one call rewrites both
lines. The replacement refers to the named groups with \g<name>, which also
lets the groups be reordered. subn returns a (new_string, count) tuple, so
[1] is the number of substitutions made.