Rewriting an immutable string

How can we rewrite an immutable string? We can't change individual characters inside a string:

>>> title = "Recipe 5: Rewriting, and the Immutable String"
>>> title[8] = ''
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment

Since this doesn't work, how do we make a change to a string?

Getting ready

Let's assume we have a string like this:

>>> title = "Recipe 5: Rewriting, and the Immutable String"

We'd like to do two transformations:

• Remove the part up to the :
• Replace the punctuation with _, and make all the characters lowercase

Since we can't replace characters in a string object, we have to work out some alternatives. There are several common things we can do, shown as follows:

• A combination of slicing...