Python User-Defined Functions 

🔍 What are User-Defined Functions in Python?

In Python, a user-defined function is a function that you create yourself to perform a specific task. Instead of relying only on built-in functions, you can define your own functions to make your code more reusable and organized.

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✨ Why Use User-Defined Functions?

• ✅ Avoid repeating code
• ✅ Improve readability
• ✅ Break complex problems into smaller parts
• ✅ Make programs modular and efficient

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🧠 Syntax of User-Defined Function

def function_name(parameters):
    """Optional docstring"""
    statement(s)
    return value

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📌 Simple Example

def greet():
    print("Hello, Welcome to Python!")

greet()

👉 Output:

Hello, Welcome to Python!

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🔢 Function with Parameters

def add(a, b):
    return a + b

print(add(5, 3))

👉 Output:

8

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🔄 Types of User-Defined Functions

1. Function Without Parameters

def message():
    print("Learning Python is fun!")

message()

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2. Function With Parameters

def greet(name):
    print("Hello", name)

greet("Prathima")

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3. Function With Return Value

def square(x):
    return x * x

print(square(4))

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4. Function with Default Parameters

def greet(name="Student"):
    print("Hello", name)

greet()
greet("Python Learner")

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🔁 Anonymous (Lambda) Functions

square = lambda x: x * x
print(square(5))

👉 Output:

25

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📦 Advantages of User-Defined Functions

• ✔ Code reusability
• ✔ Better organization
• ✔ Easy debugging
• ✔ Faster development

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⚠️ Best Practices

• Use meaningful function names
• Keep functions small and focused
• Add comments or docstrings
• Avoid too many parameters

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🚀 Real-Life Example

def calculate_total(price, quantity):
    total = price * quantity
    return total

print(calculate_total(100, 3))

👉 Output:

300

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📝 Conclusion

User-defined functions in Python are essential for writing clean, efficient, and reusable code. Mastering this concept will help you build real-world applications and improve your programming skills.

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🔑 Keywords

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