INTRO   O

PROBLEM SOLVING AND

PROGRAMMING IN PYTHON

 

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CIS 1051 - FOR LOOP

Understanding the

statement

 REPEATING Actions in Code

for

Every day life, we often repeat tasks:

 

  • Checking emails (one by one).
  • Taking steps while walking.
  • Counting down before a rocket launch.

Wouldn’t it be GREAT
to make Python
repeat actions for us?

That’s exactly what
a for loop does!

Syntax:

write Python programs that
repeat the same code execution

for variable in sequence:
    # Code to repeat 
	pass

it  allows us to execute a block of code multiple times, iterating over items in a sequence.

  • The variable takes one value from the sequence at a time.
  • The loop body runs once per item in the sequence.

Example: Printing Names in a List 

names = ["Alice", "Bob", "Charlie"]

for name in names:
    print(name)

  1. The loop picks the first name 
    ("Alice") and prints it.

  2. Then, it picks "Bob" ...

  3. Then, ...

Each iteration automatically
moves to the next item!

Example: Looping Over a String 

word = "Python"

for letter in word:
    print(letter)

What Happens?

The loop prints each letter
one at a time!
 

(a string is also a sequence of characters)

Using the range() Function

# Starts at 1, stops before 6

for num in range(1, 6):
    print(num)

How It Works

  • range(1, 6) generates
    a List [1, 2, 3, 4, 5]

We can use range(n) to repeat an action n times.

# `_` is a placeholder (we 
# don't need the variable)

for _ in range(3): 
    print("Hello!")

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