Module 11 - Python Modules

The Python Standard Library is a collection of modules that come bundled with Python. It provides a wide range of functionalities to help you perform various tasks without requiring additional installations or dependencies. The Standard Library covers diverse areas such as file handling, network programming, mathematics, string manipulation, and more.

Overview of Commonly Used Modules:

Let's explore some commonly used modules from the Python Standard Library, along with examples of their usage:

math: Provides mathematical functions and constants.

import math

print(math.sqrt(25))        # Output: 5.0
print(math.pi)              # Output: 3.141592653589793
print(math.sin(math.pi/2))  # Output: 1.0

random: Offers functions for generating random numbers and selecting random elements.

import random

print(random.randint(1, 10))          # Output: Random integer between 1 and 10
print(random.choice(['apple', 'banana', 'cherry']))  # Output: Random choice from the list

os: Provides operating system-related functions for file and directory manipulation.

import os

print(os.getcwd())          # Output: Current working directory
print(os.listdir('/path'))  # Output: List of files and directories in the given path

datetime: Allows working with dates, times, and timedeltas.

import datetime

now = datetime.datetime.now()
print(now)                  # Output: Current date and time
print(now.year)             # Output: Current year
print(now.strftime('%Y-%m-%d %H:%M:%S'))  # Output: Formatted date and time

json: Provides functions for working with JSON (JavaScript Object Notation) data.

import json

data = '{"name": "John", "age": 30}'
parsed_data = json.loads(data)
print(parsed_data['name'])   # Output: John

person = {'name': 'Alice', 'age': 25}
json_data = json.dumps(person)
print(json_data)             # Output: {"name": "Alice", "age": 25}

urllib: Offers modules for working with URLs and making HTTP requests.

import urllib.request

response = urllib.request.urlopen('https://www.example.com')
html = response.read()
print(html)                  # Output: HTML content of the webpage

These are just a few examples of the modules available in the Python Standard Library. The Standard Library contains numerous other modules covering areas such as regular expressions (re), file input/output (io), command-line arguments (argparse), and more.

To explore the Standard Library further, refer to the official Python documentation: https://docs.python.org/3/library/

The Python Standard Library is an invaluable resource that provides ready-to-use functionalities for various programming tasks. Understanding and utilizing the Standard Library will greatly enhance your ability to write efficient and powerful Python programs.

The dir() function is a powerful built-in function in Python that returns a sorted list of names in the current scope or the attributes of an object. It allows you to explore the available attributes, methods, and variables associated with an object or module, providing insight into its functionality and usage.

Usage of the dir() Function:

The general syntax for using the dir() function is as follows:

dir([object])

When called without any argument (dir()), it returns a list of names in the current local scope.
When called with an object as an argument (dir(object)), it returns a list of names associated with that object.

Examples of Using the dir() Function:

Exploring Names in the Current Local Scope:

x = 5
y = "Hello, World!"

print(dir())  # Output: ['__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'x', 'y']

In this example, the dir() function is called without any argument. It returns a list of names in the current local scope, including the predefined names (__builtins__, __doc__, __loader__, __name__, __package__, __spec__) and the variables x and y defined by the user.

Exploring Attributes and Methods of an Object:

my_list = [1, 2, 3]

print(dir(my_list))

In this example, the dir() function is called with the my_list object as an argument. It returns a list of attributes and methods associated with the list object, such as append(), clear(), count(), extend(), and more.

Using dir() with Modules:

import math

print(dir(math))

In this example, the dir() function is called with the math module as an argument. It returns a list of names associated with the math module, including mathematical functions like sqrt(), sin(), cos(), constants like pi, and more.

Using dir() with Custom Objects:

class Person:
   def __init__(self, name, age):
       self.name = name
       self.age = age

   def greet(self):
       print(f"Hello, my name is {self.name}.")

person = Person("Alice", 25)

print(dir(person))

In this example, the dir() function is called with the person object, which is an instance of the Person class. It returns a list of names associated with the person object, including the name and age attributes and the greet() method.

Common Uses of the dir() Function:

• Exploring available attributes and methods of an object to understand its functionality.
• Using it for introspection and debugging purposes.
• Dynamically accessing and manipulating object attributes or methods based on their names.

It's worth noting that the dir() function returns all the available names, including built-in attributes and methods, which may not always be relevant to your specific use case. Therefore, understanding the purpose and functionality of the object or module is crucial for interpreting the results of dir().

The dir() function is a valuable tool for exploring objects, modules, and the current local scope. By utilizing dir(), you can gain insights into the attributes and methods available, helping you effectively work with Python's built-in functionalities and your custom objects.