🐍 Python Basics & Syntax

# This is a comment - Python ignores it print("Hello, World!") # Print to console # Multiple lines print("Welcome to Python!") print("Let's learn together!")

# No type declaration needed! Python figures it out name = "Alice" # String age = 18 # Integer height = 5.6 # Float (decimal) is_student = True # Boolean (True/False) # You can change types! x = 5 # x is an integer x = "hello" # now x is a string - this is fine! # Multiple assignment a, b, c = 1, 2, 3 x = y = z = 0 # Check type print(type(age)) # print(type(height)) # # Type conversion num_str = "25" num_int = int(num_str) # Convert string to int num_float = float(num_str) # Convert to float text = str(123) # Convert number to string

# Output with print() print("Hello") print("Score:", 95) print("Name:", name, "Age:", age) # Multiple values # Formatted output name = "John" age = 20 print(f"My name is {name} and I'm {age} years old") # f-string (modern!) print("My name is {} and I'm {} years old".format(name, age)) # .format() # Input from user name = input("Enter your name: ") # Always returns a string! age = input("Enter your age: ") # This is a STRING, not a number # Convert input to number age = int(input("Enter your age: ")) # Now it's an integer score = float(input("Enter your score: ")) # Float for decimals

# Arithmetic operators a, b = 10, 3 print(a + b) # 13 (addition) print(a - b) # 7 (subtraction) print(a * b) # 30 (multiplication) print(a / b) # 3.333... (division - always float!) print(a // b) # 3 (floor division - integer) print(a % b) # 1 (remainder/modulo) print(a ** b) # 1000 (power - a to the power of b) # Comparison operators 10 > 5 # True 10 < 5 # False 10 >= 10 # True 10 == 10 # True (equal to) 10 != 5 # True (not equal to) # Logical operators True and True # True True or False # True not True # False # String operators "Hello" + " " + "World" # "Hello World" (concatenation) "Ha" * 3 # "HaHaHa" (repetition)

# If statement - NOTICE THE INDENTATION! age = 18 if age >= 18: print("You are an adult") print("You can vote") # Still inside if block print("This always runs") # Outside if block # If-elif-else score = 85 if score >= 90: grade = "A" elif score >= 80: grade = "B" elif score >= 70: grade = "C" else: grade = "F" print(f"Your grade: {grade}") # Ternary operator (one-liner) status = "Pass" if score >= 60 else "Fail" # Multiple conditions age = 20 has_license = True if age >= 18 and has_license: print("You can drive!") if age < 18 or not has_license: print("Cannot drive")

# For loop - iterate over a sequence for i in range(5): # 0, 1, 2, 3, 4 print(i) # Range with start and end for i in range(1, 6): # 1, 2, 3, 4, 5 print(i) # Range with step for i in range(0, 10, 2): # 0, 2, 4, 6, 8 print(i) # Loop through a list fruits = ["apple", "banana", "orange"] for fruit in fruits: print(fruit) # While loop count = 0 while count < 5: print(count) count += 1 # count = count + 1 # Break and continue for i in range(10): if i == 5: break # Exit loop if i % 2 == 0: continue # Skip to next iteration print(i) # Only prints odd numbers: 1, 3 # Loop with else (runs if loop completes without break) for i in range(3): print(i) else: print("Loop completed!")

# String creation text = "Hello World" text2 = 'Single quotes work too' long_text = """Multiple lines of text""" # String indexing (starts at 0!) first_char = text[0] # "H" last_char = text[-1] # "d" (negative index from end) # String slicing substring = text[0:5] # "Hello" (start:end, end not included) substring = text[:5] # "Hello" (start from beginning) substring = text[6:] # "World" (go to end) # String methods print(text.upper()) # "HELLO WORLD" print(text.lower()) # "hello world" print(text.replace("World", "Python")) # "Hello Python" print(text.split()) # ["Hello", "World"] (split into list) print(len(text)) # 11 (length) # Check if substring exists if "Hello" in text: print("Found it!")