Function

The function is the set of instructions to perform a specific task, nothing but functions.
A subprogram or a smaller part of the main program.
A block of code that performs a specific task and can be called when needed.

Purpose of Functions:

Perform specific operations.
Promote code reusability, allowing the same block of code to be used multiple times without rewriting.

Advantages of Functions

Using functions in programming provides several benefits:

Reduced Development Time: Modular code is faster to write and maintain.
Lower Memory Usage: Reusing functions avoids duplicating code.
Faster Execution: Optimized, reusable code can improve performance.
Improved Performance: Modular design enhances application efficiency.
Minimized Code Redundancy: Avoids repetitive code, making programs cleaner and easier to maintain.

Parts of Functions

Functions in Python consist of two main components:

Function Definition: Defines the function’s name, parameters, and the code block to execute.Created using the def keyword.Exists only once in the program.
Defines the function’s name, parameters, and the code block to execute.
To create function using the def keyword.
Exists only once in the program.
Function Calls: Invokes the function to execute its code.Can occur multiple times in the program.Requires a corresponding function definition, or a NameError will occur.
Invokes the function to execute its code.
Can occur multiple times in the program.
Requires a corresponding function definition, or a NameError will occur.

# Creating function def hello(): function defintion print("Hello Cedlearn") # function body hello() # function calling

Phases of Functions

Every function typically involves three phases:

Input: Accepts data (parameters or arguments) to process.
Process: Performs operations on the input data.
Output: Returns a result or produces an effect (e.g., printing, modifying data).

Types of Function

In Python, functions can be categorized into several types based on their characteristics and how they are defined. Here are the main types of functions in Python:

1. Built-in Functions

These are functions that come pre-defined with Python and are available for use without any imports. Examples include:

print()
len()
type()
sum()
min()
max()

2. User-defined Functions

These are functions that you define yourself using the def keyword. For example:

pythonCopydef greet(name): print(f"Hello, {name}!")

Also known as anonymous functions, these are small, one-line functions defined using the lambda keyword. They do not require a name and can have any number of input parameters but only one expression.

pythonCopyadd = lambda x, y: x + y

4. Recursive Functions

A function that calls itself in order to solve a problem. It's often used in problems involving recursion, like calculating factorials or performing tree/graph traversals.

pythonCopydef factorial(n): if n == 0: return 1 return n * factorial(n - 1)

5. Higher-order Functions

These are functions that take one or more functions as arguments, or return a function as a result. Common examples include map(), filter(), and reduce() from the functools module.

pythonCopydef apply_func(func, x): return func(x) result = apply_func(lambda x: x ** 2, 5)

6. Functions with Default Arguments

These functions have default values for some of their parameters, which are used if no argument is provided for those parameters.

pythonCopydef greet(name, message="Hello"): print(f"{message}, {name}!")

7. Functions with Variable-Length Arguments

Functions that can accept a variable number of arguments:

*args: Used to pass a variable number of non-keyword arguments.
**kwargs: Used to pass a variable number of keyword arguments.

Example with *args:

pythonCopydef add(*args): return sum(args)

Example with **kwargs:

pythonCopydef print_info(**kwargs): for key, value in kwargs.items(): print(f"{key}: {value}")

8. Built-in Lambda Functions

While lambda functions are user-defined, they can also be used directly within other functions like map(), filter(), and sorted() to apply functions to sequences.

pythonCopyresult = map(lambda x: x * 2, [1, 2, 3])

9. Partial Functions

These are functions that "freeze" some portion of the function’s arguments, producing a new function. This can be done using functools.partial().

pythonCopyfrom functools import partial def power(base, exponent): return base ** exponent cube = partial(power, exponent=3) print(cube(2)) # Output: 8

Each type of function serves a specific purpose and can be chosen based on the use case.