Python Basics: Common Questions, Syntax, Data Types, Control Structures, Functions, Modules, and Error Handling

Python is a high‑level, general‑purpose programming language known for its clear syntax and extensive library support, suitable for web development, data analysis, artificial intelligence, automation scripts, and many other fields.

Reasons to choose Python include its ease of learning due to a syntax that resembles natural language, wide applicability across domains, an active and large community, and cross‑platform compatibility on Windows, Linux, and macOS.

Basic Syntax

Comments: single‑line comments use # , multi‑line comments use triple quotes '''...''' or """...""" .

Variables: no type declaration is needed; assign directly, e.g., a = 10 .

Strings: enclosed in single '...' or double "..." quotes; support multi‑line and raw strings.

Data Types

Integer ( int ) – e.g., 5 .

Floating‑point ( float ) – e.g., 3.14 .

String ( str ) – e.g., "Hello" .

Boolean ( bool ) – True or False .

List ( list ) – mutable sequence, e.g., [1, 2, 3] .

Tuple ( tuple ) – immutable sequence, e.g., (1, 2, 3) .

Dictionary ( dict ) – key‑value pairs, e.g., {'name': 'Alice', 'age': 30} .

Set ( set ) – unordered collection of unique items, e.g., {1, 2, 3} .

Control Structures

Conditional statements: if , elif , else .

Loops: for loops iterate over sequences; while loops repeat while a condition holds.

Branching: execute different code blocks based on conditions.

Functions

Define a function with def , e.g., def greet(name): print(f"Hello, {name}!") .

Parameters support positional, keyword, default, and variable arguments.

Anonymous functions use lambda , e.g., lambda x: x * 2 .

Modules and Packages

A module is a file containing Python definitions and statements; import it with import module_name .

A package organizes modules and typically includes an __init__.py file.

Exception Handling

Use try...except...finally blocks to catch and handle errors.

Input/Output

Input: input() reads user input.

Output: print() displays output.

Common Built‑in Functions

Examples include len() , type() , range() , sorted() , sum() , any() , all() , etc.

Advanced Concepts

List comprehensions generate lists in a single line, e.g., [x**2 for x in range(5)] .

Generators are special iterators defined with the yield keyword.

Context managers use the with statement to manage resources such as files.

Typical Runtime Errors and Solutions

SyntaxError: invalid syntax – occurs when the code violates Python syntax rules (e.g., missing colon, mismatched parentheses). Check the highlighted line and ensure correct syntax.

IndentationError: expected an indented block – Python requires indentation to define code blocks. Add the appropriate spaces (commonly four) to the indicated lines.

NameError: name 'xxx' is not defined – a variable or name is used before being defined or misspelled. Verify the spelling and definition order.

list index out of range – attempting to access a list element beyond its length. Ensure the index is between 0 and len(list)-1 , using len() if needed.

KeyError: 'xxx' – trying to retrieve a non‑existent key from a dictionary. Use dict.get(key, default) or check key in dict before access.

TypeError: argument of type 'int' is not iterable – attempting to iterate over a non‑iterable object such as an integer. Iterate only over iterable types like lists, tuples, strings, or generators.

TypeError: xxx takes no arguments – calling a function with arguments when it expects none. Review the function definition and adjust the call accordingly.