Python For Loop

1. Basic For Loop Syntax & Range Function

The range() function allows you to generate a sequence of numbers easily, which is often used to repeat a block of code a specific number of times.

Python

# Iterate numbers from 0 to 4
for i in range(5):
    print("Count:", i)

Output: Count: 0 Count: 1 Count: 2 Count: 3 Count: 4

2. How For Loop Works (Flow)

Start Loop & Fetch Next Item from Sequence

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Are there items left in the sequence?

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TRUE → Assign item to variable & execute code block

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FALSE → Exit loop and proceed to next program statement

Real-Time Example 1: E-Commerce Inventory Stock Check

Iterate through an inventory list to identify items running low on stock.

Python

stock_levels = {"Sugar": 15, "Flour": 4, "Rice": 25, "Oil": 8}

print("Low Stock Alerts:")
for item, qty in stock_levels.items():
    if qty < 10:
        print(f"Warning: {item} is running low ({qty} units left)")

Output: Low Stock Alerts: Warning: Flour is running low (4 units left) Warning: Oil is running low (8 units left)

Real-Time Example 2: Retail Billing & Total Calculation

Calculate the grand total bill amount by summing up item prices from a cart.

Python

cart_prices = [450, 1200, 300, 850, 150]
total_bill = 0

for price in cart_prices:
    total_bill += price

print("Total Cart Amount: ₹", total_bill)

Output: Total Cart Amount: ₹ 2950

Real-Time Example 3: Student Attendance Tracker

Loop through a roster dictionary to count present students for daily logs.

Python

attendance = {"Rahul": "Present", "Priya": "Absent", "Amit": "Present", "Sneha": "Present"}
present_count = 0

for student, status in attendance.items():
    if status == "Present":
        present_count += 1

print("Total Students Present:", present_count)

Output: Total Students Present: 3

Real-Time Example 4: Employee Payroll Salary Increment

Iterate through an employee list to process annual salary revisions.

Python

salaries = [35000, 48000, 52000, 60000]
updated_salaries = []

for sal in salaries:
    new_sal = sal * 1.10  # 10% increment
    updated_salaries.append(int(new_sal))

print("Revised Salaries:", updated_salaries)

Output: Revised Salaries: [38500, 52800, 57200, 66000]

Real-Time Example 5: ATM Multi-User Balance Validation

Verify account statuses and flag accounts requiring minimum balance maintenance.

Python

account_balances = [12000, 2500, 45000, 800, 15000]

for idx, balance in enumerate(account_balances, start=1):
    if balance < 3000:
        print(f"Account {idx}: Penalty applied for low balance (₹{balance})")
    else:
        print(f"Account {idx}: Status Normal (₹{balance})")

Output: Account 1: Status Normal (₹12000) Account 2: Penalty applied for low balance (₹2500) Account 3: Status Normal (₹45000) Account 4: Penalty applied for low balance (₹800) Account 5: Status Normal (₹15000)

Real-Time Example 6: Email Domain Validation Filter

Scan a user database registration list to find corporate domain emails.

Python

email_list = ["john@gmail.com", "sarah@company.com", "admin@yahoo.com", "dave@company.com"]
corporate_users = []

for email in email_list:
    if email.endswith("@company.com"):
        corporate_users.append(email)

print("Verified Corporate Emails:", corporate_users)

Output: Verified Corporate Emails: ['sarah@company.com', 'dave@company.com']

Real-Time Example 7: Restaurant Table Booking Tracker

Loop through reservation tokens to seat waiting guests automatically.

Python

waiting_queue = ["Table-1", "Table-2", "Table-3"]

print("Seating Guests:")
for table in waiting_queue:
    print(f"Allocating {table} to next family in queue.")

Output: Seating Guests: Allocating Table-1 to next family in queue. Allocating Table-2 to next family in queue. Allocating Table-3 to next family in queue.

Real-Time Example 8: File Batch Processing Simulation

Process a batch of uploaded image file names to convert or compress formats.

Python

uploaded_files = ["photo1.png", "logo.jpg", "banner.png", "icon.svg"]

for file in uploaded_files:
    if file.endswith((".png", ".jpg")):
        print(f"Processing image compression for: {file}")
    else:
        print(f"Skipping unsupported format: {file}")

Output: Processing image compression for: photo1.png Processing image compression for: logo.jpg Processing image compression for: banner.png Skipping unsupported format: icon.svg

Real-Time Example 9: Exam Grade Analytics & Pass Counter

Analyze a list of student marks to calculate how many candidates passed.

Python

exam_scores = [78, 45, 92, 33, 60, 88, 54]
passed_students = 0

for score in exam_scores:
    if score >= 50:
        passed_students += 1

print("Total Candidates Passed:", passed_students)
print("Total Candidates Failed:", len(exam_scores) - passed_students)

Output: Total Candidates Passed: 5 Total Candidates Failed: 2

Real-Time Example 10: Bulk Rate Pricing Matrix

Generate a bulk rate pricing matrix or multiplication table for service units.

Python

base_rate = 150

print("Bulk Rate Pricing Table (1 to 5 units):")
for unit in range(1, 6):
    cost = unit * base_rate
    print(f"{unit} Unit(s) = ₹{cost}")

Output: Bulk Rate Pricing Table (1 to 5 units): 1 Unit(s) = ₹150 2 Unit(s) = ₹300 3 Unit(s) = ₹450 4 Unit(s) = ₹600 5 Unit(s) = ₹750

Summary of Python For Loops

Iteration: For loops automate repetitive tasks across any iterable sequence like lists, tuples, or dictionaries.
Range: Use `range(start, stop, step)` to loop through specific number sequences.
Efficiency: Combined with conditional statements, for loops form the core engine for data filtering, validation, and batch reporting.

🔄 What is a For Loop in Python?

Summary of Python For Loops