Python Tutorial — Learn Python Step by Step

# This is a comment — Python ignores it
print("Hello, World!")

# print() outputs text to the console
print("Hello, World!")           # String in double quotes
print('Hello, World!')           # String in single quotes (same thing)
print("Hello", "World")          # Multiple arguments separated by space
print("Hello" + " " + "World")   # String concatenation

# Print numbers and expressions
print(42)                         # Integer
print(3.14)                       # Float
print(2 + 3)                      # Expression result: 5
print("The answer is", 2 + 2)    # Mixed: The answer is 4

# Customize separator and end character
print("A", "B", "C", sep="-")    # A-B-C (default sep is space)
print("No newline", end=" ")     # Stays on same line
print("here")                     # No newline here

# f-strings (Python 3.6+) — the modern way to format output
name = "Alice"
age = 25
print(f"My name is {name} and I am {age} years old.")
# Output: My name is Alice and I am 25 years old.

# Expressions inside f-strings
print(f"Next year I will be {age + 1}.")
# Output: Next year I will be 26.

# Formatting numbers
price = 49.99
print(f"Price: ${price:.2f}")     # Price: $49.99
print(f"Percentage: {0.856:.1%}") # Percentage: 85.6%

# Single-line comment — explains the next line
print("Hello")  # Inline comment — explains this line

# Python does NOT have multi-line comments
# Use multiple # signs for multi-line notes:
# This is a
# multi-line comment

"""
Triple-quoted strings can span multiple lines.
They are technically string literals, not comments,
but are commonly used as documentation (docstrings).
"""

def greet(name):
    """This is a docstring — documents the function."""
    return f"Hello, {name}!"