The Accumulator Pattern in Python

A for loop can visit every item, but an accumulator lets it remember what happened along the way. This Block teaches the three-part pattern: choose a starting value, update it during each iteration, and use the completed result after the loop.

What you will learn:

• Build numeric totals from lists and values produced by range()
• Count items that match an if condition, including vowels in text
• Build a new string one character at a time while skipping unwanted characters
• Use += and understand its longer reassignment form
• Choose the right initial value, such as 0 or ""
• Avoid resetting, replacing, or displaying an accumulator in the wrong place

By the end, you will be able to recognize an accumulator, trace how its value changes, and use the pattern for practical loop tasks.