Modules in Python with example

import module_name   # Import entire module
from module_name import function_name   # Import specific function from a module
from module_name import *   # Import all functions from a module

In Python, a module is a file that contains Python code, including functions, classes, and variables, which can be used in other Python programs by importing them. Modules help to organize code, promote reusability, and avoid naming conflicts. Python has a vast standard library that includes many built-in modules, and you can also create your own custom modules. Let's see an example of using a built-in module and creating a custom module:

1. Using a built-in module (math module):

The `math` module provides various mathematical functions and constants. To use the functions from this module, you need to import it.

```python
import math

# Using functions from the math module
x = 3.5
y = 2

# Calculate the square root of x
sqrt_result = math.sqrt(x)
print(sqrt_result)  # Output: 1.8708286933869707

# Calculate the factorial of y
factorial_result = math.factorial(y)
print(factorial_result)  # Output: 2

# Calculate the value of pi
pi_value = math.pi
print(pi_value)  # Output: 3.141592653589793
```

2. Creating a custom module:

You can create your own Python module by defining functions, classes, or variables in a separate file. Let's create a simple module called `my_module.py`:

```python
# File: my_module.py

def greet(name):
    return f"Hello, {name}!"

def add_numbers(a, b):
    return a + b
```

Now, we can use this custom module in another Python program by importing it.

```python
import my_module

# Using functions from the custom module
name = "John"
greeting = my_module.greet(name)
print(greeting)  # Output: Hello, John!

result = my_module.add_numbers(5, 3)
print(result)  # Output: 8
```

In this example, we created a custom module `my_module.py` with two functions, `greet()` and `add_numbers()`. We then imported the module and used its functions in another Python program.

To use a module, it must be present in the same directory as the Python program or located in one of the directories listed in the `PYTHONPATH` environment variable.

Remember to create an empty file named `__init__.py` in the module's directory to make it a Python package and enable importing from submodules within the package.

Using modules is a fundamental concept in Python development, enabling code organization and reusability. It allows you to divide complex programs into smaller, manageable parts and promote efficient collaboration among developers.