Mastering Python Loops: For, While, Range, Break, Continue & More

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Understanding Python Loops

Python loops are essential for automating repetitive tasks. Whether you’re summing numbers, iterating through lists, or processing user input, loops make your code efficient, readable, and scalable. This guide explains Python loops in detail with examples, beginner-friendly explanations, and advanced tips.

Python provides two main types of loops:

1. For Loop – used to iterate over sequences like lists, tuples, strings, or ranges.
2. While Loop – runs as long as a condition remains True.

For Loop Example

# List of numbers
nums = [1, 2, 3, 4, 5]

# Loop through each number in the list
for num in nums:
    print(f"Number is: {num}")

Explanation:

• num takes each value in nums one by one.
• for loops are best when you know the number of iterations or want to iterate through a collection.

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While Loop Example

# Initialize variable
i = 1

# Loop continues as long as i <= 5
while i <= 5:
    print(f"Value of i: {i}")
    i += 1  # Increment i to avoid infinite loop

Explanation:

• while loops are used when you don’t know the number of iterations in advance.
• Loop stops when the condition (i <= 5) becomes False.

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Difference Between for and while Loops

Feature	For Loop	While Loop
Iteration	Iterates over a sequence (list, tuple, string, range)	Iterates until a condition is False
Use case	When the number of iterations is known	When iterations depend on dynamic conditions
Increment	Automatic if using range()	Must be manually done in the loop
Risk	Less risk of infinite loop	Higher risk of infinite loop if condition not handled

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Range Function

range() generates a sequence of numbers, which is commonly used with for loops.

# Numbers from 0 to 4
for i in range(5):
    print(i)

# Numbers from 1 to 9
for i in range(1, 10):
    print(i)

# Numbers from 1 to 5 skipping 1 each time
for i in range(1, 6, 2):
    print(i)

Explanation:

• range(stop) → 0 to stop-1
• range(start, stop) → start to stop-1
• range(start, stop, step) → increments by step

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Break and Continue

Break

Stops the loop immediately.

for i in range(1, 6):
    if i == 3:
        break  # Stop the loop when i is 3
    print(i)

Output:

1
2

Explanation: Loop stops when condition matches.

Continue

Skips the current iteration and continues with the next one.

for i in range(1, 6):
    if i == 3:
        continue  # Skip printing 3
    print(i)

Output:

1
2
4
5

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Difference Between break and continue

Keyword	Effect
break	Exits the loop completely
continue	Skips the current iteration and continues

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Pass Statement

pass does nothing but acts as a placeholder. Useful when the syntax requires a statement but you don’t want to write code yet.

for i in range(5):
    pass  # Placeholder, does nothing

print("End of program")

Explanation: Prevents syntax errors for empty loops, functions, or conditionals.

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Else in Loops

Python allows else with loops. It executes only if the loop completes normally (not terminated by break).

For Loop Else Example

nums = [1, 2, 3]
for num in nums:
    print(num)
else:
    print("Loop finished without break")

While Loop Else Example

i = 1
while i <= 3:
    print(i)
    i += 1
else:
    print("While loop finished normally")

Explanation:

• If a break occurs, the else block is skipped.
• Useful for searching algorithms when you want to know if a value wasn’t found.

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Practical Examples

Sum of Numbers Using For Loop

n = int(input("Enter a number: "))
total = 0
for i in range(1, n + 1):
    total += i
print(f"Sum of first {n} numbers is {total}")

Factorial Using While Loop

n = int(input("Enter a number: "))
fact = 1
i = 1
while i <= n:
    fact *= i
    i += 1
print(f"Factorial of {n} is {fact}")

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Happy Learning !