Hello World in Python – Your First Program

print("Hello, World!")

# Printing different types of data
print("Hello, World!")       # string
print(42)                    # integer
print(3.14)                  # float
print(True)                  # boolean

# Printing nothing (blank line)
print()

# Printing multiple items separated by a space
print("Name:", "Alice")
print("Age:", 25)
print("Score:", 98.5)

# sep: changes the separator between values (default is a space)
print("Python", "is", "awesome")             # Python is awesome
print("Python", "is", "awesome", sep="-")    # Python-is-awesome
print("Python", "is", "awesome", sep="")     # Pythonisawesome
print(2024, 12, 25, sep="/")                 # 2024/12/25

# end: changes what is printed at the end (default is newline \n)
print("Hello", end=" ")
print("World")                               # Hello World (on one line)

print("Loading", end="")
print(".", end="")
print(".", end="")
print(".")                                   # Loading...

# Step 1: Create a file named hello.py
# Step 2: Add your code to the file
# Step 3: Run it from the terminal

python3 hello.py

# On Windows, you might use:
python hello.py

# This is a full-line comment
print("Hello, World!")  # This is an inline comment

# You can use comments to explain complex logic:
# Multiply speed by time to get distance
distance = 60 * 2.5  # speed=60 km/h, time=2.5 hours
print(distance)       # 150.0

# Use comments to temporarily disable code during debugging:
# print("This line won't run")
print("This line will run")

# Method 1: Multiple single-line comments
# This program calculates the area of a rectangle
# Author: Alice
# Date: 2024-01-15

# Method 2: Triple-quoted string (used as a block comment)
"""
This program demonstrates basic Python output.
It uses the print() function to display messages.
Triple quotes can span multiple lines.
"""

# Docstring at the start of a function:
def greet(name):
    """Return a greeting message for the given name."""
    return f"Hello, {name}!"

print(greet("Alice"))  # Hello, Alice!

name = "Alice"
age = 25
score = 98.765

# Method 1: Concatenation (joining strings with +)
print("Name: " + name + ", Age: " + str(age))

# Method 2: % formatting (older style)
print("Name: %s, Age: %d" % (name, age))

# Method 3: str.format() method
print("Name: {}, Age: {}".format(name, age))

# Method 4: f-strings (RECOMMENDED — modern and readable)
print(f"Name: {name}, Age: {age}")
print(f"Score: {score:.2f}")     # limit to 2 decimal places → 98.77
print(f"Age next year: {age + 1}")  # expressions work inside {}

# \n = newline
print("Line 1\nLine 2\nLine 3")

# \t = tab
print("Name:\tAlice")
print("Age:\t25")

# \\ = literal backslash
print("C:\\Users\\Alice\\Documents")

# \" and \' = quotes inside strings
print("She said \"Hello!\"")
print('It\'s a great day!')

# Raw strings (r prefix) — backslashes are literal
print(r"C:\Users\Alice\no_escape_here")

# SyntaxError: Missing parentheses
# print "Hello"   ← Python 2 style, fails in Python 3

# SyntaxError: Missing closing quote
# print("Hello)   ← string not closed

# NameError: Calling a function with wrong capitalization
# Print("Hello")  ← Python is case-sensitive; it's print(), not Print()

# TypeError: Mixing string and number without conversion
# print("Age: " + 25)  ← Cannot concatenate str and int

# ✅ Fix for TypeError:
print("Age: " + str(25))   # convert int to string first
print(f"Age: {25}")        # or use f-string (handles it automatically)

# Program 1: Personal introduction
name = "Alice"
age = 25
city = "New York"

print("=" * 30)
print("    PERSONAL PROFILE")
print("=" * 30)
print(f"  Name : {name}")
print(f"  Age  : {age}")
print(f"  City : {city}")
print("=" * 30)

# Program 2: Simple receipt
item1_name = "Coffee"
item1_price = 3.50
item2_name = "Muffin"
item2_price = 2.75
total = item1_price + item2_price

print(f"{item1_name:<15} ${item1_price:.2f}")
print(f"{item2_name:<15} ${item2_price:.2f}")
print("-" * 22)
print(f"{'Total':<15} ${total:.2f}")