Lesson 18: Loop Control (break and continue)

Learn how to use break and continue to control loops, skip or exit iterations, combine with conditionals, and apply common looping patterns effectively.

Introduction

You know how to loop through lists with for loops. You know how to repeat until a condition changes with while loops.

But sometimes you need more control. You need to exit a loop early when you find what you're looking for. Or skip certain items without processing them.

This is what break and continue do.

break exits the loop immediately. continue skips to the next iteration.

They give you fine-grained control over loop execution.

Lesson Overview

This section contains a general overview of topics you will learn in this lesson.

Using break to exit loops early
Using continue to skip iterations
When to use each
Combining with conditionals
Common patterns

The break Statement

break exits the loop immediately, skipping any remaining iterations.

sheets = ["A-101", "A-102", "S-101", "S-102", "M-101"]

# Find first structural sheet
for sheet in sheets:
    if sheet.startswith("S"):
        print(f"Found structural sheet: {sheet}")
        break  # Stop searching

Output:

Found structural sheet: S-101

The loop stops as soon as it finds "S-101". It never checks "S-102" or "M-101".

How break Works

When Python hits break, it exits the loop immediately and continues with the code after the loop.

for i in range(1, 11):
    if i == 5:
        print("Stopping at 5")
        break
    print(i)

print("Loop finished")

Output:

1
2
3
4
Stopping at 5
Loop finished

The loop processes 1, 2, 3, 4, then hits the break at 5 and exits.

Architectural Example: Finding a Specific Sheet

sheets = ["A-101", "A-102", "A-201", "A-202", "S-101"]
target = "A-201"
found = False

print(f"Searching for {target}...")

for sheet in sheets:
    print(f"  Checking {sheet}")
    if sheet == target:
        print(f"  Found it!")
        found = True
        break

if not found:
    print(f"{target} not found")

Output:

Searching for A-201...
  Checking A-101
  Checking A-102
  Checking A-201
  Found it!

It stops checking once it finds the target. No need to check the remaining sheets.

break with while Loops

break works with while loops too.

revision = 0

while True:  # Infinite loop
    revision += 1
    print(f"Revision {revision}")

    if revision >= 5:
        print("Approved")
        break  # Exit the loop

print("Done")

Output:

Revision 1
Revision 2
Revision 3
Revision 4
Revision 5
Approved
Done

while True creates an infinite loop, but break exits it when the condition is met.

The continue Statement

continue skips the rest of the current iteration and moves to the next one.

room_areas = [450.5, 380.2, 520.8, 410.3, 395.7]

# Process only compliant rooms
for area in room_areas:
    if area < 400:
        continue  # Skip non-compliant rooms

    print(f"Processing room: {area}m²")

Output:

Processing room: 450.5m²
Processing room: 520.8m²
Processing room: 410.3m²

The rooms with areas below 400 are skipped. The code after continue doesn't run for those items.

How continue Works

When Python hits continue, it skips the rest of the loop body and goes to the next iteration.

for i in range(1, 11):
    if i % 2 == 0:  # Skip even numbers
        continue
    print(i)

Output:

Even numbers (2, 4, 6, 8, 10) are skipped.

Architectural Example: Processing Issued Sheets Only

sheets = ["A-101", "A-102", "A-201", "A-202"]
issued = ["A-101", "A-201"]

print("Processing issued sheets:")

for sheet in sheets:
    if sheet not in issued:
        continue  # Skip draft sheets

    print(f"  Exporting {sheet}")
    print(f"  Sending to contractor")

Output:

Processing issued sheets:
  Exporting A-101
  Sending to contractor
  Exporting A-201
  Sending to contractor

Draft sheets (A-102, A-202) are skipped entirely.

break vs continue

break:

Exits the entire loop
Use when you found what you're looking for
Use when a condition means you should stop entirely

continue:

Skips to the next iteration
Use when you want to skip certain items
Use when some items don't need processing

# break - stop at first failure
for area in room_areas:
    if area < 400:
        print("Found non-compliant room, stopping check")
        break
    print(f"{area}m²: OK")

# continue - skip failures, check everything
for area in room_areas:
    if area < 400:
        continue  # Skip this one
    print(f"{area}m²: OK")

Common Patterns

Pattern 1: Early Exit on Error

sheets = ["A-101", "A-102", "INVALID", "A-201"]

print("Validating sheets:")

for sheet in sheets:
    if len(sheet) < 5:
        print(f"Error: Invalid sheet number '{sheet}'")
        break
    print(f"  {sheet}: Valid")

print("Validation stopped")

Output:

Validating sheets:
  A-101: Valid
  A-102: Valid
Error: Invalid sheet number 'INVALID'
Validation stopped

Pattern 2: Skip Invalid Data

room_areas = [450.5, -1, 520.8, 0, 410.3]

print("Valid room areas:")

for area in room_areas:
    if area <= 0:
        continue  # Skip invalid data
    print(f"  {area}m²")

Output:

Valid room areas:
  450.5m²
  520.8m²
  410.3m²

Pattern 3: Find First Match

floor_names = ["Basement", "Ground", "First", "Second"]
target = "First"

for i, floor in enumerate(floor_names):
    if floor == target:
        print(f"'{target}' is at index {i}")
        break
else:
    print(f"'{target}' not found")

Output:

'First' is at index 2

Pattern 4: Process Subset

sheets = ["A-101", "A-102", "S-101", "A-201", "M-101"]

print("Architectural sheets only:")

for sheet in sheets:
    if not sheet.startswith("A"):
        continue  # Skip non-architectural

    print(f"  {sheet}")

Output:

Architectural sheets only:
  A-101
  A-102
  A-201

Real Architectural Workflows

Example 1: Finding Non-Compliant Rooms

room_data = [
    {"name": "Office 1", "area": 420},
    {"name": "Office 2", "area": 380},
    {"name": "Office 3", "area": 450},
    {"name": "Office 4", "area": 395},
]

minimum_area = 400

print("Checking for first non-compliant room:")

for room in room_data:
    if room["area"] >= minimum_area:
        continue  # Skip compliant rooms

    # First non-compliant room found
    print(f"Found: {room['name']} ({room['area']}m²)")
    break

print("Check complete")

Output:

Checking for first non-compliant room:
Found: Office 2 (380m²)
Check complete

Example 2: Export Only Changed Sheets

sheets = ["A-101", "A-102", "A-201", "A-202"]
unchanged = ["A-102", "A-202"]

print("Exporting modified sheets:")

for sheet in sheets:
    if sheet in unchanged:
        print(f"  {sheet}: Skipped (unchanged)")
        continue

    print(f"  {sheet}: Exported")

Output:

Exporting modified sheets:
  A-101: Exported
  A-102: Skipped (unchanged)
  A-201: Exported
  A-202: Skipped (unchanged)

Example 3: Stop at Budget Limit

items = [
    {"name": "Windows", "cost": 50000},
    {"name": "Doors", "cost": 30000},
    {"name": "Flooring", "cost": 40000},
    {"name": "Lighting", "cost": 25000},
]

budget = 100000
spent = 0

print("Adding items to project:")

for item in items:
    if spent + item["cost"] > budget:
        print(f"\\nBudget limit reached at {spent}")
        print(f"Cannot add: {item['name']}")
        break

    spent += item["cost"]
    print(f"  {item['name']}: ${item['cost']} (Total: ${spent})")

print(f"\\nFinal total: ${spent}")

Output:

Adding items to project:
  Windows: $50000 (Total: $50000)
  Doors: $30000 (Total: $80000)

Budget limit reached at 80000
Cannot add: Flooring

Final total: $80000

The else Clause with Loops

Loops can have an else block that runs if the loop completes without hitting break.

sheets = ["A-101", "A-102", "A-201"]
target = "S-101"

for sheet in sheets:
    if sheet == target:
        print(f"Found {target}")
        break
else:
    print(f"{target} not found")

Output:

S-101 not found

If break is hit, the else doesn't run. If the loop completes normally, else runs.

This is useful for search patterns:

# Find first non-compliant room
for area in room_areas:
    if area < 400:
        print(f"Non-compliant: {area}m²")
        break
else:
    print("All rooms compliant")

Common Mistakes

Using continue when you mean break

# Wrong - continues checking all rooms
for area in room_areas:
    if area < 400:
        print("Found non-compliant room")
        continue  # Keeps looping!

If you want to stop at the first non-compliant room, use break, not continue.

break/continue in wrong place

# Wrong - break is outside the if
for area in room_areas:
    if area < 400:
        print("Non-compliant")
    break  # This always breaks on first iteration!

break needs to be inside the condition if you want conditional exit.

Forgetting what continue does

for area in room_areas:
    if area < 400:
        continue
    # This code runs for compliant rooms only
    print(f"{area}m²: Processing")

After continue, the code below it doesn't run for that iteration.

When NOT to Use break/continue

Don't use continue when filtering:

# Awkward
compliant = []
for area in room_areas:
    if area < 400:
        continue
    compliant.append(area)

# Clearer
compliant = []
for area in room_areas:
    if area >= 400:
        compliant.append(area)

The second version is more straightforward.

Don't use break when you can use a condition:

# Awkward
count = 0
for i in range(100):
    if count >= 10:
        break
    count += 1

# Clearer
for i in range(10):
    # Just loop 10 times

Use the right tool. If you know the count, use range.

Assignment

Create a new file called loop_control.py
Find first match with break:
- List: sheets = ["A-101", "A-102", "S-101", "S-102", "M-101"]
- Find and print the first sheet starting with "S"
- Use break to stop searching
Skip invalid data with continue:
- List: areas = [450.5, -1, 520.8, 0, 410.3, -5]
- Print only positive areas
- Use continue to skip invalid values
Search with else:
- List: sheets = ["A-101", "A-102", "A-201"]
- Search for "A-150"
- Use break if found
- Use else to print "not found"
Stop at threshold:
- List: costs = [5000, 3000, 4000, 2500, 6000]
- Budget: 10000
- Add costs until budget exceeded
- Use break when limit reached
- Print total spent
Process subset:
- List: sheets = ["A-101", "A-102", "S-101", "A-201", "M-101"]
- Process only sheets starting with "A"
- Use continue to skip others
- Print processed sheets
Early exit on error:
- List: areas = [450, 420, -50, 380]
- Check each area
- If any negative, print error and break
- Otherwise print "All valid"
Real scenario - Compliance check:
- Rooms: [{"name": "Office 1", "area": 420}, {"name": "Office 2", "area": 380}, {"name": "Office 3", "area": 450}]
- Find first non-compliant room (< 400)
- Print its name and area
- Stop checking after first failure

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Knowledge Check

The following questions are an opportunity to reflect on key topics in this lesson.

<a class="knowledge-check-link" href="#the-break-statement">What does break do?</a>
<a class="knowledge-check-link" href="#the-continue-statement">What does continue do?</a>
<a class="knowledge-check-link" href="#break-vs-continue">When should you use break vs continue?</a>
<a class="knowledge-check-link" href="#the-else-clause-with-loops">What does the else clause do with loops?</a>
<a class="knowledge-check-link" href="#common-mistakes">What happens if break is outside the if block?</a>

Additional Resources

This section contains helpful links to related content. It isn't required, so consider it supplemental.

Python's break and continue documentation covers loop control in detail
Real Python's guide to loop control provides additional examples and use cases

Updated on Mar 27, 2026

Getting Started with Python

Variables, Data Types and Expressions

Lists and Collections

Control Flow - Decisions

Loops - Repeating Work

Lesson 18: Loop Control (break and continue)

Introduction

Lesson Overview

The break Statement

How break Works

Architectural Example: Finding a Specific Sheet

break with while Loops

The continue Statement

How continue Works

Architectural Example: Processing Issued Sheets Only

break vs continue

Common Patterns

Pattern 1: Early Exit on Error

Pattern 2: Skip Invalid Data

Pattern 3: Find First Match

Pattern 4: Process Subset

Real Architectural Workflows

Example 1: Finding Non-Compliant Rooms

Example 2: Export Only Changed Sheets

Example 3: Stop at Budget Limit

The else Clause with Loops

Common Mistakes

Using continue when you mean break

break/continue in wrong place

Forgetting what continue does

When NOT to Use break/continue

Assignment

Knowledge Check

Additional Resources