REFRESHING PYTHON BASICS FOR INTERVIEW

PYTHON BASICS AND ITS FEATURES

What is Python?

Python is a popular, high-level, and interpreted programming language known for its readability
and ease of use. Key features include:

 Open-source and cross-platform: Python is free to use and runs on various operating
systems like Windows, MacOS, and Linux.
 Large standard library: Python comes with a vast collection of modules and packages
that help with tasks such as file I/O, system calls, and even Internet protocols.
 Interactive mode: Python provides an interactive shell that allows you to test code
snippets quickly.
 Whitespace for readability: Uses indentation to define code blocks, enhancing
readability.
 Multiple paradigms: Supports object-oriented, procedural, and functional programming
paradigms.
 Code readability: Python’s syntax is clear and easy to understand, making it an excellent
choice for beginners and experienced programmers alike.

Companies Using Python

Python is used by many leading companies for diverse applications:

 Google: Uses Python for web services, data analysis, and machine learning.
 Facebook: Utilizes Python for backend services and data analysis.
 Netflix: Relies on Python for data analysis, recommendation systems, and machine
learning.
 Amazon: Employs Python in order fulfillment, recommendation systems, and machine
learning.
 Microsoft: Uses Python for data analysis, automation, and machine learning.
 IBM: Implements Python in data science, AI, and cloud services.
 NASA: Utilizes Python for data analysis, image processing, and automation tasks.

Python Basics

 Introduction to Python: Learning about Python’s history, applications, and environment
setup.
 Data Types and Variables: Understanding and using different data types in Python.
 IDEs for Python: Getting familiar with Integrated Development Environments like
IDLE and PyCharm for writing and running Python code.

Data Types in Python

 Integers: Whole numbers, e.g., 42, -7.
 Floats: Decimal numbers, e.g., 3.14159, -0.01.

,  Strings: Sequences of characters, e.g., "Hello, World!".
 Lists: Ordered, mutable collections, e.g., [1, 2, 3].
 Tuples: Ordered, immutable collections, e.g., (1, 2, 3).
 Dictionaries: Unordered collections of key-value pairs, e.g., {'name': 'Alice', 'age': 30}.
 Sets: Unordered, mutable collections, e.g., {1, 2, 3}.

Type Conversions in Python

Convert between data types using built-in functions:

 Integer to float: float(42) converts the integer 42 to the float 42.0.
 Float to integer: int(3.14) converts the float 3.14 to the integer 3.
 String to integer: int('42') converts the string '42' to the integer 42.
 Integer to string: str(42) converts the integer 42 to the string '42'.

Strings in Python

 Creating Strings:
o Single quotes: 'Hello'
o Double quotes: "Hello"
o Triple quotes for multi-line strings: '''Hello''' or """Hello"""
 Slicing Strings: Extract substrings using slicing notation, e.g., my_string[0:5] extracts
characters from index 0 to 4.
 String Functions:
o len(): Returns the length of the string.
o upper(): Converts all characters in the string to uppercase.
o lower(): Converts all characters in the string to lowercase.
o strip(): Removes leading and trailing whitespace.
o find(): Returns the index of the first occurrence of a substring.
 String Operators:
o +: Concatenates two strings.
o *: Repeats the string a specified number of times.
o []: Accesses characters in the string by index.
o <, >, ==: Compares strings.
o in: Checks if a substring exists within a string.

Lists and Tuples in Python

 Creating Lists and Tuples:
o Lists: [1, 2, 3]
o Tuples: (1, 2, 3)
 Accessing Elements: Use indices, e.g., my_list[0] or my_tuple[1].
 Updating Elements (Lists only): my_list[0] = 'new_value'
 Deleting Elements (Lists only): del my_list[0]
 List Functions: