Pet Services: Making and Reading Lists

# ------------------------------------------
# Pet Service Booking System
# ------------------------------------------
# This program collects dog information,
# calculates grooming cost based on size and service,
# applies age-based modifiers,
# and prints a clear booking summary.
# ------------------------------------------

# ---- Chunk A: Welcome and Instructions ----

print("Welcome to the Dog Grooming Booking System.")
print("This program is for DOGS only.")
print("Size categories: small (0–10kg), medium (10–25kg), large (25kg+).")
print("Services available: bath, haircut, full.")
print("--------------------------------------------")

# ---- Chunk B: Collect Basic Inputs ----

dog_name = input("Enter your dog's name: ")
dog_breed = input("Enter your dog's breed: ")

# ---- Chunk C: Validate Age Input Using a While Loop ----

# We keep asking until the user gives a sensible number.

while True:
dog_age_input = input("Enter your dog's age in years: ")

```
# Check if the input is a number
if dog_age_input.isdigit():
    dog_age = int(dog_age_input)

    # Age cannot be negative
    if dog_age >= 0:
        break
    else:
        print("Age cannot be negative. Try again.")
else:
    print("Please enter a valid whole number for age.")
```

# ---- Validate Dog Size ----

# This while loop ensures size is one of the allowed options.

valid_sizes = ["small", "medium", "large"]

while True:
dog_size = input("Enter dog size (small / medium / large): ").lower()

```
if dog_size in valid_sizes:
    break
else:
    print("Invalid size. Please type small, medium, or large.")
```

# ---- Display Services Using a For Loop ----

# Instead of writing 3 separate print statements,

# we loop through a list.

services = ["bath", "haircut", "full"]

print("\nAvailable services:")
for service_option in services:
print("-", service_option)

# ---- Validate Service Choice ----

while True:
service = input("Choose a service: ").lower()

```
if service in services:
    break
else:
    print("Invalid service. Please choose from the list above.")
```

# ---- Chunk D: Calculate Base Cost ----

# Base cost depends on BOTH service and size.

if service == "bath":
if dog_size == "small":
base_cost = 20
elif dog_size == "medium":
base_cost = 25
else:
base_cost = 30

elif service == "haircut":
if dog_size == "small":
base_cost = 30
elif dog_size == "medium":
base_cost = 35
else:
base_cost = 40

else:  # full grooming
if dog_size == "small":
base_cost = 45
elif dog_size == "medium":
base_cost = 50
else:
base_cost = 60

# ---- Chunk E: Apply Age Modifiers ----

total_cost = base_cost  # Start with base cost

# Puppy discount

if dog_age < 1:
total_cost = total_cost * 0.9  # Reduce by 10%

# Senior dog fee

if dog_age >= 10:
total_cost = total_cost + 5

# ---- Chunk F: Output Booking Summary ----

# We store summary lines in a list and print them using a for loop.

summary_lines = [
"\n----- Booking Summary -----",
f"Dog name: {dog_name}",
f"Breed: {dog_breed}",
f"Age: {dog_age} years",
f"Size category: {dog_size}",
f"Service selected: {service}",
f"Base cost: ${base_cost:.2f}",
f"Final total cost: ${total_cost:.2f}"
]

for line in summary_lines:
print(line)

print("----------------------------")

A single list can affect multiple parts of the program. That is useful because the data is stored in one place. But it also means you need to think carefully about which rules depend on that data.

Program categories that are meant to stay fixed are often good tuple candidates. In this lesson, valid_sizes is a reasonable example to test as a tuple.

Check your brackets carefully. Lists use [ ]. Tuples use ( ). Make sure you didn’t mix them.

That is expected unless you also add new pricing logic. The list controls what gets shown and validated. The if / elif / else pricing section still controls the actual cost.

That is normal. Tuples are not designed to grow using append(). That is one of the reasons tuples are useful for fixed data.

Ask yourself: what would the code look like without the list? Usually the answer is “longer, messier, and more repetitive.”