一些网站的密码由数字和字母组成，另一些必须是数字、字母和特殊符号的组合，还有一些必须有一个大写字母，小写字母和数字组成。

Some Web sites require passwords with numbers and letters, others require numbers, letters and special characters, and still others require a capital letter, a lower-case letter and then a number.

youdao

如果一个元素的有效值是“red”、“blue”和“green”，我们想让用户对这些值可以使用任意的大写字母和小写字母组合。

If the valid values for an element are "red," "blue," and "green," we'd like to let our users use any combination of upper - and lowercase letters for those values.

youdao

写一个读取文件的程序，把每一行拆分成一个个词，去掉空白和标点符号，然后把所有单词都转换成小写字母的。

Write a program that reads a file, breaks each line into words, strips whitespace and punctuation from the words, and converts them to lowercase.

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Now, once you know each of those, you can now do 25 more upper case letters and 25 more lower case letters then there are some other stuff like punctuation and things you see on the keyboard.

一旦你知道两者中的任何一个，你就知道了另外25个,大写字母和小写字母,标点和在键盘上的,各种符号也有ASCII码。

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