python range, break, continue, assert and loop
Python Range, Break, Continue, Assert & Loop Practice Exercises
Introduction
When working with loops, Python provides several useful tools:
range()→ Generate sequences of numbersbreak→ Stop a loop immediatelycontinue→ Skip the current iterationassert→ Check assumptions during program execution
These are commonly used in:
- Loops
- Data processing
- Validation
- Automation scripts
- Testing and debugging
The range() Function
What is range()?
The range() function generates a sequence of numbers.
It is commonly used with for loops.
Example:
for i in range(5):
print(i)
Output:
0
1
2
3
4
Why Use range()?
Without range():
print(1)
print(2)
print(3)
print(4)
print(5)
With range():
for i in range(1, 6):
print(i)
Output:
1
2
3
4
5
Less code and easier maintenance.
Syntax of range()
range(stop)
or
range(start, stop)
or
range(start, stop, step)
range(stop)
Starts from:
0
Stops before:
stop
Example:
for i in range(5):
print(i)
Output:
0
1
2
3
4
range(start, stop)
Example:
for i in range(1, 6):
print(i)
Output:
1
2
3
4
5
range(start, stop, step)
Example:
for i in range(0, 11, 2):
print(i)
Output:
0
2
4
6
8
10
Negative Step
Example:
for i in range(10, 0, -1):
print(i)
Output:
10
9
8
7
6
5
4
3
2
1
Counting Backward
for i in range(5, -1, -1):
print(i)
Output:
5
4
3
2
1
0
Converting range() to List
numbers = list(range(1, 6))
print(numbers)
Output:
[1, 2, 3, 4, 5]
Checking Length of range()
r = range(1, 11)
print(len(r))
Output:
10
Accessing Values from range()
r = range(10)
print(r[0])
print(r[5])
Output:
0
5
Using range() with Multiplication Table
for i in range(1, 11):
print(5 * i)
Output:
5
10
15
20
25
30
35
40
45
50
Common range() Mistakes
Mistake 1: Stop Value Included
❌ Wrong Expectation
range(1, 5)
Expected:
1 2 3 4 5
Actual:
1 2 3 4
The stop value is excluded.
Mistake 2: Wrong Step Direction
❌ Wrong
range(10, 1, 1)
Output:
Nothing
✅ Correct
range(10, 1, -1)
Mistake 3: Forgetting range() in for Loop
❌ Wrong
for i in 5:
print(i)
Output:
TypeError
✅ Correct
for i in range(5):
print(i)
Break Statement
What is break?
The break statement immediately terminates a loop.
When Python encounters break:
Loop Stops Immediately
Basic Example
for i in range(10):
if i == 5:
break
print(i)
Output:
0
1
2
3
4
How break Works
Loop Running
|
V
Condition True?
|
Yes
|
break
|
Loop Ends
Real-Life Example: Search Operation
numbers = [10, 20, 30, 40]
for num in numbers:
if num == 30:
print("Found")
break
Output:
Found
No need to continue searching.
Password System Example
attempts = 0
while True:
password = input("Password: ")
if password == "python123":
print("Access Granted")
break
attempts += 1
Loop stops when password is correct.
Nested Loop Example with break
for row in range(3):
for col in range(3):
if col == 1:
break
print(row, col)
Output:
0 0
1 0
2 0
Break only affects the inner loop.
Continue Statement
What is continue?
continue skips the current iteration and moves to the next one.
Basic Example
for i in range(5):
if i == 2:
continue
print(i)
Output:
0
1
3
4
How continue Works
Current Iteration
|
Condition True?
|
Yes
|
continue
|
Skip Remaining Code
|
Next Iteration
Example: Print Odd Numbers
for i in range(1, 11):
if i % 2 == 0:
continue
print(i)
Output:
1
3
5
7
9
Example: Skip a Character
for char in "PYTHON":
if char == "H":
continue
print(char)
Output:
P
Y
T
O
N
Difference Between break and continue
| Feature | break | continue |
|---|---|---|
| Stops Loop | Yes | No |
| Skips Iteration | No | Yes |
| Ends Loop Completely | Yes | No |
| Continues Loop | No | Yes |
Example Comparison
break
for i in range(5):
if i == 2:
break
print(i)
Output:
0
1
continue
for i in range(5):
if i == 2:
continue
print(i)
Output:
0
1
3
4
Common break & continue Mistakes
Mistake 1: Unexpected Loop Exit
for i in range(10):
break
Output:
Loop stops immediately
Mistake 2: Infinite Loop with continue
❌ Wrong
i = 1
while i <= 5:
if i == 3:
continue
print(i)
i += 1
Output:
Infinite Loop
Reason:
i += 1 never executes when i == 3.
✅ Correct
i = 1
while i <= 5:
if i == 3:
i += 1
continue
print(i)
i += 1
Assert Statement
What is assert?
The assert statement is used to test assumptions.
Syntax:
assert condition
If condition is:
True → Program Continues
False → AssertionError
Basic Example
age = 20
assert age >= 18
print("Eligible")
Output:
Eligible
Assertion Failure
age = 15
assert age >= 18
Output:
AssertionError
Assert with Message
age = 15
assert age >= 18, "Must be 18 or older"
Output:
AssertionError: Must be 18 or older
Real-Life Example
balance = 1000
withdraw = 500
assert withdraw <= balance, "Insufficient Funds"
print("Transaction Successful")
Output:
Transaction Successful
Another Example
username = "admin"
assert username != "", "Username cannot be empty"
Why Use assert?
Useful for:
- Testing
- Debugging
- Verifying assumptions
- Detecting bugs early
Common Assert Mistakes
Mistake 1: Using assert for User Validation
❌ Avoid
assert password == "admin"
Assertions can be disabled in some Python execution modes.
Use:
if password != "admin":
print("Invalid Password")
for user validation.
Mistake 2: Wrong Condition
❌ Wrong
assert age < 18
When requirement is:
age >= 18
Practice Exercises on Looping
Exercise 1
Print numbers from 1 to 20 using a for loop.
Solution
for i in range(1, 21):
print(i)
Exercise 2
Print even numbers between 1 and 50.
Solution
for i in range(2, 51, 2):
print(i)
Exercise 3
Print odd numbers between 1 and 50.
Solution
for i in range(1, 51):
if i % 2 == 0:
continue
print(i)
Exercise 4
Print multiplication table of 9.
Solution
for i in range(1, 11):
print(9 * i)
Exercise 5
Calculate sum of numbers from 1 to 100.
Solution
total = 0
for i in range(1, 101):
total += i
print(total)
Output:
5050
Exercise 6
Find first number divisible by both 7 and 11 between 1 and 100.
Solution
for i in range(1, 101):
if i % 7 == 0 and i % 11 == 0:
print(i)
break
Output:
77
Exercise 7
Count vowels in a word.
Solution
word = "education"
count = 0
for char in word:
if char.lower() in "aeiou":
count += 1
print(count)
Output:
5
Exercise 8
Reverse Countdown
Solution
for i in range(10, 0, -1):
print(i)
print("Launch!")
Exercise 9
Print a Triangle Pattern
Solution
for row in range(1, 6):
for col in range(row):
print("*", end=" ")
print()
Output:
*
* *
* * *
* * * *
* * * * *
Exercise 10
Find factorial of 5.
Solution
factorial = 1
for i in range(1, 6):
factorial *= i
print(factorial)
Output:
120
Quick Revision
| Concept | Purpose |
|---|---|
| range() | Generate numbers |
| break | Stop loop |
| continue | Skip iteration |
| assert | Verify assumptions |
| Nested Loop | Loop inside loop |
| range(start, stop, step) | Custom sequences |
Summary
| Statement | Description |
|---|---|
| range() | Creates number sequences |
| break | Terminates loop immediately |
| continue | Skips current iteration |
| assert | Tests conditions during execution |
| AssertionError | Raised when assert fails |
| Negative Step | Used for reverse counting |
| Loop Practice | Improves logic-building skills |
Master range(), break, continue, and assert before moving to Functions because these concepts appear frequently in real-world Python code, coding interviews, automation scripts, testing, and software development.