Python Loop Examples with Real-World Order Processing

The best way to master loops is to solve real problems. All examples below work on one list of e-commerce orders, the kind of data you get from a database or an API. Each problem is solved with a for loop and, where useful, a while loop.

The Sample Data

orders = [
    {"id": 101, "amount": 5000, "status": "Completed"},
    {"id": 102, "amount": 0, "status": "Cancelled"},
    {"id": 103, "amount": 15000, "status": "Completed"},
    {"id": 104, "amount": 2000, "status": "Pending"},
    {"id": 105, "amount": 25000, "status": "Completed"},
    {"id": 106, "amount": 5000, "status": "Completed"},
    {"id": 107, "amount": 13000, "status": "Pending"},
    {"id": 108, "amount": 4500, "status": "Completed"},
    {"id": 109, "amount": 14500, "status": "Cancelled"}
]

Example 1: Process the large orders using for loop

Process only the orders >= 10000 and ignore the cancelled orders

for order in orders:

    if order["status"] == "Cancelled":
        continue

    if order["amount"] >= 10000:
        print("Large Order:", order["id"], order["amount"])

Example 2: Same requirement using WHILE loop

i = 0
while i < len(orders):
    order = orders[i]
    i = i + 1           # increment before continue, otherwise infinite loop

    if order["status"] == "Cancelled":
        continue

    if order["amount"] >= 10000:
        print("Large Order:", order["id"], order["amount"])

Example 3: Calculate total revenue of Completed orders using for loop

total_revenue = 0
for order in orders:
    if order["status"] == "Completed":
        total_revenue = total_revenue + order["amount"]

print("Total Revenue:", total_revenue)

Example 4: Calculate total revenue of Completed orders using WHILE loop

total_revenue = 0
i = 0
while i < len(orders):
    if orders[i]["status"] == "Completed":
        total_revenue = total_revenue + orders[i]["amount"]
    i = i + 1

print("Total Revenue:", total_revenue)

Example 5: Count the orders by status using for loop

completed_count = 0
pending_count = 0
cancelled_count = 0

for order in orders:
    if order["status"] == "Completed":
        completed_count = completed_count + 1
    elif order["status"] == "Pending":
        pending_count = pending_count + 1
    elif order["status"] == "Cancelled":
        cancelled_count = cancelled_count + 1

print("Completed:", completed_count)
print("Pending:", pending_count)
print("Cancelled:", cancelled_count)

Example 6: Count the orders by status using a dictionary (FOR loop)

status_count = {}
for order in orders:
    status = order["status"]
    status_count[status] = status_count.get(status, 0) + 1

print(status_count)

Example 7: Find the first Pending order and stop searching (FOR loop + break)

for order in orders:
    if order["status"] == "Pending":
        print("First Pending Order:", order["id"], order["amount"])
        break

Example 8: Search an order by id using WHILE loop + break

search_id = 105
i = 0
found = False

while i < len(orders):
    if orders[i]["id"] == search_id:
        print("Order Found:", orders[i])
        found = True
        break
    i = i + 1

if not found:
    print("Order", search_id, "not found")

Example 9: For-else -> else block runs only when loop is NOT broken

search_id = 200
for order in orders:
    if order["id"] == search_id:
        print("Order Found:", order)
        break
else:
    print("Order", search_id, "not found")

Example 10: Find the highest and lowest order amount (ignore Cancelled)

highest_order = None
lowest_order = None

for order in orders:
    if order["status"] == "Cancelled":
        continue

    if highest_order is None or order["amount"] > highest_order["amount"]:
        highest_order = order

    if lowest_order is None or order["amount"] < lowest_order["amount"]:
        lowest_order = order

print("Highest Order:", highest_order["id"], highest_order["amount"])
print("Lowest Order:", lowest_order["id"], lowest_order["amount"])

Example 11: Collect the large order ids into a new list

large_order_ids = []
for order in orders:
    if order["status"] != "Cancelled" and order["amount"] >= 10000:
        large_order_ids.append(order["id"])

print("Large Order Ids:", large_order_ids)

Example 12: Same as above using List Comprehension (one line for loop)

large_order_ids = [order["id"] for order in orders
                   if order["status"] != "Cancelled" and order["amount"] >= 10000]

print("Large Order Ids:", large_order_ids)

Example 13: Print orders with serial number using enumerate()

for index, order in enumerate(orders, start=1):
    print(index, "->", order["id"], order["amount"], order["status"])

Example 14: Apply 10% discount on Completed orders >= 10000

for order in orders:
    if order["status"] == "Completed" and order["amount"] >= 10000:
        discount = order["amount"] * 10 / 100
        final_amount = order["amount"] - discount
        print("Order:", order["id"], "Amount:", order["amount"],
              "Discount:", discount, "Final Amount:", final_amount)

Example 15: Process Pending orders one by one until none left (WHILE loop)

pending_orders = [order for order in orders if order["status"] == "Pending"]

while pending_orders:                       # runs while list is not empty
    order = pending_orders.pop(0)           # take the first pending order
    print("Processing Pending Order:", order["id"], "-> marked as Completed")

print("Pending orders left:", len(pending_orders))

Example 16: Stop processing once the daily target of 40000 is reached (WHILE loop)

daily_target = 40000
collected = 0
i = 0

while i < len(orders) and collected < daily_target:
    if orders[i]["status"] == "Completed":
        collected = collected + orders[i]["amount"]
        print("Added Order:", orders[i]["id"], "Collected so far:", collected)
    i = i + 1

print("Target reached:", collected >= daily_target)

Example 17: Group the orders by status (nested data using for loop)

grouped_orders = {}
for order in orders:
    status = order["status"]
    if status not in grouped_orders:
        grouped_orders[status] = []
    grouped_orders[status].append(order["id"])

for status, ids in grouped_orders.items():
    print(status, "->", ids)

Example 18: Process orders in reverse order (latest order first)

for order in reversed(orders):
    print(order["id"], order["amount"])

Example 19: Same reverse processing using WHILE loop

i = len(orders) - 1
while i >= 0:
    print(orders[i]["id"], orders[i]["amount"])
    i = i - 1

Example 20: Sort orders by amount (highest first) and print top 3

sorted_orders = sorted(orders, key=lambda order: order["amount"], reverse=True)

for order in sorted_orders[:3]:
    print("Top Order:", order["id"], order["amount"])