Learn Python and Libraries: Key Differences from C# and PHP

This guide is tailored for developers coming from C# and PHP backgrounds who want to learn Python efficiently. We’ll focus on the syntax and concepts unique to Python and how they differ from your current experience.

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✅ 1. Python Syntax is Clean and Indentation-Based

if x > 5:
    print("Greater")
else:
    print("Smaller or Equal")

• ❌ No curly braces {}
• ✅ Indentation determines blocks (like scope)

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✅ 2. Variables: No Type Declaration

x = 10
name = "John"
is_valid = True

• ❌ No int, string, or bool required
• ✅ Dynamic typing

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✅ 3. Function Definitions Are Simpler

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

• ❌ No public, void, function keywords
• ✅ Uses def and optional type hints:

def add(a: int, b: int) -> int:
    return a + b

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✅ 4. String Formatting with f-Strings

name = "Alice"
print(f"Hello, {name}!")

• Replaces string.Format() (C#) or "Hello $name" (PHP)

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✅ 5. List, Tuple, Set, Dictionary

my_list = [1, 2, 3]        # Like array
my_tuple = (1, 2, 3)       # Immutable list
my_set = {1, 2, 3}         # No duplicates
my_dict = {"a": 1, "b": 2} # Like associative array or Dictionary

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✅ 6. None Instead of null

value = None

• ✅ Python’s equivalent to null (PHP/C#)

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✅ 7. Loops: for in Collections

for item in ["a", "b", "c"]:
    print(item)

• ✅ No classic for (int i=0; ...)
• Use range() for index-based iteration:

for i in range(5):
    print(i)  # 0 to 4

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✅ 8. elif, is, in, not in, with

elif

Chained else if condition:

if x == 0:
    pass
elif x == 1:
    print("One")
else:
    print("Other")

is

Checks identity (not just equality):

if x is None:
    print("x is None")

in / not in

Used to check membership:

if "a" in ["a", "b", "c"]:
    print("found")

with

Used for context managers (e.g., opening files):

with open("file.txt") as f:
    contents = f.read()

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✅ 9. pass Statement

The pass keyword is a placeholder for future code. It does nothing when executed, but it lets you write empty blocks that won’t throw errors.

def future_feature():
    pass  # To be implemented later

if condition:
    pass  # Reserved for logic

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✅ 10. try/except Instead of try/catch

try:
    risky_function()
except Exception as e:
    print(e)

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✅ 11. No Semi-Colons

print("Hello")

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✅ 12. List Comprehension (Powerful Python Feature)

squares = [x * x for x in range(10)]

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✅ 13. Importing Libraries

import math
print(math.sqrt(16))

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✅ 14. Built-in Data Types in Python

# Numbers
num = 42           # int
pi = 3.14          # float
z = 2 + 3j         # complex

# Sequence
s = "hello"        # str
b = b"hello"       # bytes
l = [1, 2, 3]      # list
t = (1, 2, 3)      # tuple
r = range(5)       # range

# Sets
myset = {1, 2, 3}  # set
fset = frozenset([1, 2, 3])

# Mapping
mydict = {"key": "value"}

# Boolean
flag = True

# NoneType
empty = None

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✅ 15. Defining Classes and Objects

class Person:
    species = "Human"  # Class variable

    def __init__(self, name, age):
        self.name = name        # Instance variable
        self.age = age
        self.status = "active"

    def greet(self):
        print(f"Hello, I am {self.name}, {self.age} years old")

    def is_active(self):
        return self.status == "active"

p = Person("Alice", 30)
print(p.species)
print(p.name)
p.greet()

• ✅ Uses __init__ as constructor
• ✅ self is like this in C#/PHP
• ✅ Supports both class-level and instance-level variables

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✅ 16. Inheritance and Interface-Like Behavior

class Animal:
    def speak(self):
        print("Some sound")

class Dog(Animal):
    def speak(self):
        print("Woof")

# Polymorphism
animal = Dog()
animal.speak()  # Woof

Python does not have a built-in interface keyword. Instead, it uses duck typing: “If it walks like a duck and quacks like a duck…”

For strict interface enforcement:

from abc import ABC, abstractmethod

class PaymentGateway(ABC):
    @abstractmethod
    def authenticate(self):
        pass

    @abstractmethod
    def process_payment(self, amount):
        pass

class PayPal(PaymentGateway):
    def authenticate(self):
        print("Authenticating PayPal user...")

    def process_payment(self, amount):
        print(f"Processing ${amount} via PayPal")

class Stripe(PaymentGateway):
    def authenticate(self):
        print("Authenticating Stripe user...")

    def process_payment(self, amount):
        print(f"Processing ${amount} via Stripe")

# Example usage
gateway: PaymentGateway = Stripe()
gateway.authenticate()
gateway.process_payment(100)

• ✅ ABC is the base class for defining abstract base classes
• ✅ @abstractmethod ensures method is overridden

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🔧 Popular Python Libraries for Beginners

Library	Purpose
math	Basic math functions
random	Random number generation
datetime	Date/time manipulation
os	Operating system commands
sys	System-level operations
json	JSON encode/decode
requests	HTTP requests
pandas	Data analysis (like Excel)
numpy	Scientific computing (arrays)