Python Basics: Comments, Variables, Random Numbers

Python Comments

• Comments are used to explain code, enhance readability, and prevent execution during testing.
• A comment starts with # and is ignored by Python.
• Comments can also be placed at the end of lines.
• Multiline comments can be created by adding # at the beginning of each line or using triple quotes for string literals.

Python Variables

• Variables act as containers for storing data values and are created upon first assignment.
• No explicit declaration is necessary; variables can change type dynamically (e.g., from integer to string).
• Casting is possible to enforce specific data types using functions like str(), int(), and float().
• The data type of a variable can be determined using the type() function.
• Variable names are case-sensitive.

Random Numbers

• To generate random numbers, Python utilizes the built-in random module.
• Example usage: import random followed by print(random.randrange(1, 10)) generates a random number between 1 and 9.

Strings and Arrays

• Strings in Python are arrays of bytes representing Unicode characters; single characters are considered strings of length 1.
• Elements of a string can be accessed using square brackets.
• The length of a string is obtained with the len() function.
• Use the in keyword to check for specific phrases or characters within a string.

String Manipulation

• Slicing allows extraction of a substring from a string using index ranges.
• .upper() converts a string to uppercase, while .lower() converts it to lowercase.
• The strip() method removes leading and trailing whitespace from a string.
• Strings can be concatenated using the + operator, with an option to include spaces.

String Formatting

• F-Strings, introduced in Python 3.6, allow embedding expressions inside string literals prefixed with 'f'.
• Placeholders within f-strings can contain variables, operations, and modifiers for formatted output (e.g., {value:.2f} for two decimal places).

Python Conditions and If Statements

• Python supports standard logical conditions such as ==, !=, <, >, <=, >=.
• The if statement executes code based on evaluated conditions.
• elif allows multiple conditions to be checked in sequence, while else handles cases when no preceding conditions are true.
• Indentation is crucial for defining code blocks; it replaces the need for curly braces.
• Conditional expressions can be expressed in a single line using shorthand syntax.

Logical Operators

• and, or, and not are logical operators used to combine or negate conditions in statements.
• Nested if statements are permitted, allowing complex conditional logic within the defined scope.
• The pass statement can be used as a placeholder in an empty if statement to avoid syntax errors.