April Python Bootcamp Day 11

What is a Function?

A function is a reusable block of code that performs a specific task.

def greet():
    print("Hello, World!")

greet()

Once defined, a function can be called multiple times:

greet()
greet()

This avoids repetition and makes your code cleaner.

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 Function Syntax

def func_name(val1, val2):  # parameters
    # code
    pass

• def → keyword to define function
• func_name → function name
• val1, val2 → parameters
• pass → placeholder

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 Parameters vs Arguments

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

greet("Piyush")

• name → parameter (definition time)
• "Piyush" → argument (calling time)

Important rule:

Number of parameters = Number of arguments (unless defaults are used)

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 Functions with Return Value

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

result = add(5, 3)
print(result)

Key difference:

• print() → displays output
• return → sends value back for reuse

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 Types of Arguments

1. Positional Arguments

Order matters.

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

add(5, 3)

Output:

3
5
8

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2. Keyword Arguments

Order does not matter.

def example(name, age):
    print(f"My name is {name} and my age is {age}")

example(age=30, name="Piyush")

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3. Default Arguments

Used when values are not provided.

def example(name="Not Known", age="I Don't know"):
    print(f"My name is {name} and my age is {age}")

example("Rafish")
example("Rahul", 45)
example()

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4. Variable-Length Arguments (*args)

Used when number of inputs is unknown.

def total(*nums):
    return sum(nums)

print(total(1, 2, 3, 4, 5))

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5. Keyword Variable-Length Arguments (**kwargs)

Accepts multiple key-value pairs.

def details(**data):
    print(data)

details(name="Piyush", age=30, phone=12345)

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 Key Observations

• Functions can accept any data type (even True, strings, etc.)
• Flexible argument handling makes functions powerful
• Widely used in APIs, backend systems, automation, and ML pipelines

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 Assignments (Based on Today’s Concepts)

 Basic Level

1. Create a function that prints "Hello Python"
2. Write a function that takes a name and prints a greeting
3. Create a function that adds two numbers and returns the result
4. Call a function multiple times and observe output
5. Pass different data types (int, string, boolean) to a function

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 Intermediate Level

1. Create a function using positional arguments and observe order impact
2. Create a function and call it using keyword arguments
3. Write a function with default parameters and test all cases
4. Create a function using *args to find the sum of numbers
5. Modify *args function to return maximum value

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 Advanced Level

1. Create a function using **kwargs and print all key-value pairs
2. Build a function that accepts both *args and **kwargs
3. Create a function that validates input before processing
4. Write a function that returns multiple values (sum, average)
5. Implement a mini user profile system using **kwargs

Example idea:

def profile(**data):
    for key, value in data.items():
        print(f"{key} : {value}")

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 Summary

• Functions make code reusable and structured
• return is essential for real-world applications
• Argument types provide flexibility (*args, **kwargs)
• Understanding parameter behavior is critical for debugging