Building complicated strings from lists of characters

How can we make complicated changes to an immutable string? Can we assemble a string from individual characters?

In most cases, the recipes we've already seen give us a number of tools for creating and modifying strings. There are yet more ways in which we can tackle the string manipulation problem. In this recipe, we'll look at using a list object as a way to decompose and rebuild a string. This will dovetail with some of the recipes in Chapter 4, Built-In Data Structures Part 1: Lists and Sets.

Getting ready

Here's a string that we'd like to rearrange:

>>> title = "Recipe 5: Rewriting an Immutable String"

We'd like to do two transformations:

• Remove the part before:
• Replace the punctuation with _ and make all the characters lowercase

We'll make use of the string module:

>>> from string import whitespace, punctuation...