SB Character classification

Section 3.10 Character classification

It is often helpful to examine a character and test whether it is upper- or lowercase, or whether it is a character or a digit. The string module provides several constants that are useful for these purposes. One of these, string.digits is equivalent to “0123456789”. It can be used to check if a character is a digit using the in operator.

The string string.ascii_lowercase contains all of the ascii letters that the system considers to be lowercase. Similarly, string.ascii_uppercase contains all of the uppercase letters. string.punctuation comprises all the characters considered to be punctuation. Run the following:

import string print(string.ascii_lowercase) print(string.ascii_uppercase) print(string.digits) print(string.punctuation)

For more information consult the string module documentation (see Global Module Index

http://docs.python.org/py3k/py-modindex.html

Note 3.10.1.

More About ASCII

ASCII is abbreviated from American Standard Code for Information Interchange. As computers store data in numeric values, for each character (words, punctuations, etc) a specific number is assigned to represent it. This process is called character encoding. In order to exchange informations between different computers, a set of standards were needed, from which ASCII was born.

ASCII contains 128 characters, where each character is assigned with a specific number. For instance uppercase alphabet starts from A = 65, while lowercase alphabet starts from a = 97 and continues as b=98, c=99, so on. Due to its limited size, this standard is replaced by Unicode which contains thousands of characters, however still useful to understand and work on encoding.

Note 3.10.2.

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