Machine Learning and Programming with Python for Beginners : A Gentle 2 in 1 Introduction to Machine Learning for Programming Beginners by CAMPBELL SAM

Author:CAMPBELL, SAM
Language: eng
Format: epub
Published: 2024-01-18T00:00:00+00:00

Functions and Modules

4.1 Writing and Calling Functions

In Python, functions are reusable blocks of code that perform a specific task. They help organize code, make it more readable, and allow for efficient code reuse. Here's an overview of writing and calling functions in Python:

Writing Functions:

To define a function in Python, use the def keyword, followed by the function name and parameters. The function body is indented.

Example:

def greet(name): """This function greets the person passed as a parameter."""print(f"Hello, {name}!")

You can also specify default values for parameters:

def greet(name="Guest"): print(f"Hello, {name}!")

Calling Functions:

To call a function, use its name followed by parentheses. If the function has parameters, provide the values inside the parentheses.

Example:

greet("Alice")

Return Statement:

Functions can return values using the return statement. This allows the function to produce a result that can be used elsewhere in the code.

Example:

def add_numbers(a, b): """This function adds two numbers and returns the result."""return a + b result = add_numbers(5, 3) print(result)

Keyword Arguments:

When calling a function, you can use keyword arguments to explicitly match values with parameter names. This can enhance code readability.

Example:

greet(name="Bob")

Arbitrary Number of Arguments:

You can use *args and **kwargs to handle an arbitrary number of positional and keyword arguments.

Example:

def print_args(*args, **kwargs): print("Positional arguments:", args) print("Keyword arguments:", kwargs) print_args(1, 2, 3, name="Alice", age=30)

Lambda Functions:

Lambda functions, or anonymous functions, are defined using the lambda keyword. They are often used for short, simple operations.

Example:

multiply = lambda x, y: x * y result = multiply(4, 5) print(result)

Docstrings:

Document your functions using docstrings (triple-quoted strings) to provide documentation about the function's purpose, parameters, and return values.

Example:

def square(number): """ This function squares the given number. :param number: The number to be squared. :type number: int or float :return: The square of the input number. :rtype: int or float """ return number ** 2

Scope of Variables:

Be aware of variable scope. Variables defined inside a function are local to that function, while variables defined outside functions are global.

Example:

global_variable = 10 def print_global(): print(global_variable) print_global()

Understanding how to write and call functions is fundamental to Python programming. It promotes code modularity, reusability, and maintainability. As you continue to develop your Python skills, you'll find that effective use of functions enhances the structure and readability of your code.

4.2 Function Parameters and Return Values

In Python, function parameters allow you to pass values to functions, and return values allow functions to provide results back to the calling code. Here's an in-depth look at function parameters and return values:

Function Parameters:

1. Positional Parameters:

The most common type of parameters where values are assigned based on their position in the function call.

Example:

def greet(name, greeting): print(f"{greeting}, {name}!") greet("Alice", "Hello")

2. Default Parameters:

Parameters can have default values, allowing you to call a function without providing a value for that parameter.

Example:

def greet(name, greeting="Hello"): print(f"{greeting}, {name}!") greet("Bob")

3. Keyword Arguments:

You can use the parameter names explicitly when calling a function, allowing for more readable code.

Example:

greet(greeting="Hi", name="Charlie")

4. Arbitrary Number of Arguments:

You can use *args to accept any number of positional arguments.

Example:

def print_args(*args): print("Arguments:", args) print_args(1, 2, 3, "four")

5. Keyword Arguments as Dictionary:

You can use **kwargs to accept any number of keyword arguments.

Example:

def print_kwargs(**kwargs): print("Keyword arguments:", kwargs) print_kwargs(name="David", age=25, city="New York")

Return Values:

1.

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