Andromeda
Note

for Loops (Python)

Definition

A control flow statement used to iterate over a sequence (such as a list, tuple, or range) and execute a block of code for each item in that sequence.

Why It Matters

The for loop is the foundational engine of algorithmic scaling; it allows a single programmer to perform work on millions of data points simultaneously, transforming coding from manual data entry into the construction of automated labor systems.

Core Concepts

  • Iteration: The process of repeating an action for every element in a set.
  • The range() Function:
    • range(stop): Iterates from 0 up to (but not including) stop.
    • range(start, stop): Iterates from start up to (but not including) stop.
    • range(start, stop, step): Iterates using a specific increment.
    • Negative Step: Using a negative step (e.g., range(5, -1, -1)) allows for counting down.
  • Indentation: Python uses whitespace to define the “scope” of the loop. Code intended to repeat must be indented.
  • Example Usage:
# Iterating over a list
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(f"I like {fruit}s")

# Using range() for numerical iteration
for i in range(1, 4):
    print(f"Attempt #{i}")
  • Loop Control: break and continue function identically to their use in while loops.

Connected Concepts

Connected notes