The first set, [A-Za-z], represents any letter.

第一个集合 [A-Za-z] 表示所有字母。

youdao

The second set, [A-Za-z0-9_]{2,9}, represents a series of at least two and up to nine of any letter, any digit, and the underscore.

第二个集合 [A-Za-z0-9_]{2,9} 表示由至少 2 个至多 9 个任意字母、数字和划线组成的序列。

youdao

You can use [: digit:] in place of [0-9], and [: alpha:] is a more portable replacement for [-a-za-z0-9_]. For example, you can strip all punctuation from a string by using the statement.

您可以使用[：digit：]代替[0 - 9]，并且[：alpha：]是比[- a - zA - z 0 - 9 _]更具有可移植性的替代者。

youdao

He was born to a Canadian father and a mother who is part of the Dunne-za tribe.

VOA: special.2009.11.13

Each party in this community-organized Za Krizen ( following the cross ) procession is led by a cross-bearer who walks barefoot or in socks, never resting.

UNESCO: Culture