Regular Expressions 101

Explanation
Pro

^start of line

Group name_chs(?P<name_chs>(?:[\u3007\u4e00-\u9fff\u3400-\u4dbf\uf900-\ufaff]+)(?=\.))?

?repeats the group contents below at most once:

Non-Capturing Group(?:[\u3007\u4e00-\u9fff\u3400-\u4dbf\uf900-\ufaff]+)

Character Class[\u3007\u4e00-\u9fff\u3400-\u4dbf\uf900-\ufaff]+

+matches at least one character from the set below:

\u3007the literal 〇 (3007₁₆ / 30007₈ / 12295₁₀)

\u4e00-\u9fffone character from 一 (19968₁₀) to 鿿 (40959₁₀)

\u3400-\u4dbfone character from 㐀 (13312₁₀) to 䶿 (19903₁₀)

\uf900-\ufaffone character from 豈 (63744₁₀) to 﫿 (64255₁₀)

Positive Lookahead(?=\.)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group name_en(?P<name_en>\S+)

\S+any character that is not Unicode whitespace, repeated at least once

.any Unicode character (except for line terminators)

Sthe literal S (83₁₀ / 123₈ / 53₁₆) (case sensitive)

Group season(?P<season>\d{2})

\d{2}a Unicode decimal digit, repeated exactly 2 times

Ethe literal E (69₁₀ / 105₈ / 45₁₆) (case sensitive)

Group episode(?P<episode>\d{2})

\d{2}a Unicode decimal digit, repeated exactly 2 times

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

No unit tests

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25 tokens

^(?P<name_chs>(?:[\u3007\u4e00-\u9fff\u3400-\u4dbf\uf900-\ufaff]+)(?=\.))?(?P<name_en>\S+).S(?P<season>\d{2})E(?P<episode>\d{2})

There are no unit tests.