Python BEGINNERPython Fundamentals
Complete guide to Python programming basics and core concepts
10 min read
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Table of Contents
Setup & Basics
Installation & Running Python
Setting up Python and running programs
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💡 Use python3 explicitly on systems with both Python 2 and 3
⚡ Virtual environments isolate project dependencies
📌 Always use requirements.txt for dependency management
🔍 Python is case-sensitive and uses indentation for blocks
Variables & Data Types
Python variable declaration and basic data types
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💡 Python uses dynamic typing - variables can change types
⚡ Use type hints for better code documentation
📌 None is Python's null value
🔍 Variables are references to objects in memory
Strings & Formatting
String Operations
String manipulation and methods
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💡 Strings are immutable - operations return new strings
⚡ Use slicing for substring extraction
📌 Negative indices count from the end
🔍 String methods don't modify the original string
String Formatting
Modern string formatting techniques
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💡 f-strings are fastest and most readable
⚡ Use Template for untrusted user input
📌 Format specifiers: .2f (float), :04d (padding), :, (thousands)
🔍 f-strings allow any Python expression inside {}
Data Structures
Lists
Ordered, mutable sequences
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💡 Lists are mutable and ordered
⚡ List comprehensions are faster than loops
📌 Use copy() for shallow copies, deepcopy() for nested
🔍 Negative indices and slicing work like strings
Tuples
Ordered, immutable sequences
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💡 Tuples are immutable - use for fixed collections
⚡ Tuple unpacking simplifies multiple assignments
📌 Single element tuple needs trailing comma: (1,)
🔍 Named tuples provide readable attribute access
Dictionaries
Key-value pairs (hash maps)
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💡 Dictionaries are unordered until Python 3.7+
⚡ Use get() to avoid KeyError exceptions
📌 Dictionary keys must be immutable (str, int, tuple)
🔍 defaultdict and Counter simplify common patterns
Sets
Unordered collections of unique elements
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💡 Sets automatically remove duplicates
⚡ Membership testing is O(1) - very fast
📌 Sets are unordered - no indexing
🔍 frozenset is immutable and can be a dict key
Control Flow
Conditionals
if, elif, else statements
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💡 Python uses indentation for blocks, not braces
⚡ Ternary operator for simple if-else expressions
📌 Empty collections evaluate to False
🔍 Use "is" for None checks: if x is None
Loops
for and while loops
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💡 for-else runs if loop completes without break
⚡ enumerate() adds index to iterations
📌 zip() stops at shortest sequence
🔍 range(start, stop, step) for custom ranges
Functions
Function Basics
Defining and calling functions
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💡 *args for variable positional, **kwargs for keyword args
⚡ Use type hints for better code clarity
📌 Docstrings document function purpose and usage
🔍 * forces remaining arguments to be keyword-only
Lambda & Higher-Order Functions
Anonymous functions and functional programming
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💡 Lambda for simple, one-line functions
⚡ List comprehensions often clearer than map/filter
📌 Decorators modify function behavior
🔍 Functions are first-class objects in Python
Classes & OOP
Class Basics
Object-oriented programming fundamentals
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💡 __init__ is the constructor method
⚡ @property creates computed attributes
📌 @classmethod for alternative constructors
🔍 self refers to the instance, cls to the class
Inheritance & Polymorphism
Class inheritance and method overriding
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💡 super() calls parent class methods
⚡ ABC enforces implementation of abstract methods
📌 Multiple inheritance creates diamond problem
🔍 MRO determines method resolution order
File I/O & Exceptions
File Operations
Reading and writing files
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💡 Always use "with" for automatic file closing
⚡ pathlib provides modern path handling
📌 JSON for structured data, CSV for tabular
🔍 Binary mode for non-text files
Exception Handling
Handling errors gracefully
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💡 Catch specific exceptions, not bare except
⚡ finally always runs, even with return
📌 Custom exceptions inherit from Exception
🔍 Use assert for debugging, not production
Modules & Packages
Importing & Creating Modules
Module system and package management
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💡 Use virtual environments for project isolation
⚡ __init__.py makes a folder a Python package
📌 Avoid "from module import *" for clarity
🔍 __all__ controls what's exported with import *
Advanced Features
Generators & Iterators
Memory-efficient iteration
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💡 Generators produce values lazily, saving memory
⚡ yield pauses function and returns value
📌 Generator expressions like list comp but with ()
🔍 Generators are one-time use, then exhausted
Decorators
Function and class decorators
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💡 Decorators modify function behavior without changing code
⚡ @wraps preserves original function metadata
📌 Stack decorators - applied bottom to top
🔍 @lru_cache caches function results
Context Managers
Resource management with "with" statement
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💡 Context managers ensure cleanup with __exit__
⚡ @contextmanager simplifies creation
📌 suppress() ignores specific exceptions
🔍 ExitStack manages dynamic number of contexts
Best Practices & Tips
Pythonic Code
Writing idiomatic Python
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💡 Follow PEP 8 style guide
⚡ Use built-in functions and comprehensions
📌 EAFP over LBYL for Python style
🔍 Zen of Python: import this
Performance Tips
Optimizing Python code
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💡 Profile first, optimize bottlenecks only
⚡ Built-in functions are implemented in C
📌 Use appropriate data structures for the task
🔍 Consider NumPy/Pandas for numerical work