Variables and Data Types

A variable associates a name with a value.

username = "student"
attempts = 3
is_authorized = False

Common types

• str for text.
• int and float for numbers.
• bool for true/false state.
• list for ordered mutable values.
• tuple for ordered fixed values.
• dict for key-value records.
• set for unique values.

ports = [22, 80, 443]
service = {"port": 443, "name": "https"}

Conversion and validation

User input is text. Validate it before converting:

raw = input("Port: ").strip()
if raw.isdigit():
    port = int(raw)
    print(port)
else:
    print("Enter a number")

Choose descriptive names and avoid storing secrets directly in source code.