Dive Into Python 3

CHAPTER 6 ■ CLOSURES AND GENERATORS

95

A File of Patterns

You’ve factored out all the duplicate code and added enough abstractions so that the pluralization rules

are defined in a list of strings. The next logical step is to take these strings and put them in a separate file,

in which they can be maintained separately from the code that uses them.

First, let’s create a text file that contains the rules you want (see Listing 6-11). No fancy data

structures, just whitespace-delimited strings in three columns. Let’s call it plural4-rules.txt.

Listing 6-11. Rules in a File

[sxz]$ $ es

[^aeioudgkprt]h$ $ es

[^aeiou]y$ y$ ies

$ $ s

Now let’s see how you can use this rules file (see Listing 6-12).

Listing 6-12. Reading the Rules

import re

def ...