Using strings

Since Python strings are immutable, they're an excellent example of functional programming objects. A Python string module has a number of methods, all of which produce a new string as the result. These methods are pure functions with no side effects.

The syntax for string method functions is postfix, where most functions are prefix. This means that complex string operations can be hard to read when they're commingled with conventional functions.

When scraping data from a web page, we might have a cleaner function that applies a number of transformations to a string to clean up the punctuation and return a Decimal object for use by the rest of the application. This will involve a mixture of prefix and postfix syntax.

It might look like the following command snippet:

from decimal import *
def clean_decimal(text):
    if text is None: return text
    try:
        return Decimal(text.replace("$", "").replace(",", ""))
    except InvalidOperation...