官方https://docs.python.org/3.4/library/string.html#string.Formatter
6.1. string — Common string operations
Source code: Lib/string.py
6.1.1. String constants
The constants defined in this module are:
- string.ascii_letters
-
The concatenation of the ascii_lowercase and ascii_uppercase constants described below. This value is not locale-dependent.
- string.ascii_lowercase
-
The lowercase letters 'abcdefghijklmnopqrstuvwxyz'. This value is not locale-dependent and will not change.
- string.ascii_uppercase
-
The uppercase letters 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'. This value is not locale-dependent and will not change.
- string.digits
-
The string '0123456789'.
- string.hexdigits
-
The string '0123456789abcdefABCDEF'.
- string.octdigits
-
The string '01234567'.
- string.punctuation
-
String of ASCII characters which are considered punctuation characters in the C locale.
- string.printable
-
String of ASCII characters which are considered printable. This is a combination of digits, ascii_letters, punctuation, and whitespace.
- string.whitespace
-
A string containing all ASCII characters that are considered whitespace. This includes the characters space, tab, linefeed, return, formfeed, and vertical tab.