python - [\w\d] 中的\d 不是多余的吗？

Question

我正在读一本书，看到很多这样的例子:

(?P<email>
[\w\d.+-]+ # username
@
([\w\d.]+\.)+ # domain name prefix
(com|org|edu) # limit the allowed top-level domains
)

自 \w意味着 [a-zA-Z0-9_] , \d意味着 [0-9] , \d是 \w 的子集.
那么，那些 "\d"不是多余的吗？请有人确认我的理解是正确的，因为这让我发疯。

Answer 1

是的，这是多余的，而且很简单 \w也能正常工作。见 https://docs.python.org/2/library/re.html

\d

When the UNICODE flag is not specified, matches any decimal digit; this is equivalent to the set [0-9]. With UNICODE, it will match whatever is classified as a decimal digit in the Unicode character properties database.

\w

When the LOCALE and UNICODE flags are not specified, matches any alphanumeric character and the underscore; this is equivalent to the set [a-zA-Z0-9_]. With LOCALE, it will match the set [0-9_] plus whatever characters are defined as alphanumeric for the current locale. If UNICODE is set, this will match the characters [0-9_] plus whatever is classified as alphanumeric in the Unicode character properties database.