Notes Python Basics and features

Character Set

• Letters: A-Z, a-z
• Digits: 0-9
• Special Symbols: space +-*/()~!@#$%^&[]{},;:”‘<.>/`
• Whitespaces: Blank space, Enter, Tab
• Other Characters: ASCII and Unicode characters

Tokens

• Keywords: Reserved words with special meaning (e.g., if, else, while).
• Identifiers: Names for variables, functions, classes, etc. (e.g., my_var, calculateTotal)
  • Rules: Must start with a letter or underscore, case-sensitive, no spaces or special characters except underscores.
• Literals: Fixed values (e.g., 123, "hello")
  • Types: String, Numeric, Boolean, Special (None), Literal Collections
• Operators: Symbols that perform operations (e.g., +, -, *, /)
• Punctuators: Symbols used for program structure (e.g., (), {}, ,, ;)

Keywords

• Reserved words with special meanings. Examples: def, return, import.

Identifiers

• Forming Rules:
  • Can be a long sequence of letters and digits
  • Start with a letter or underscore
  • Case-sensitive
  • Cannot be a keyword
  • No special characters except underscore

Literals

• String Literals: Enclosed in single or double quotes (e.g., "hello", '123')
• Numeric Literals:
  • Integer: Decimal (e.g., 1234), Octal (e.g., 0o10), Hexadecimal (e.g., 0xF)
  • Floating Point: Decimal (e.g., 12.5), Exponent (e.g., 1.5e2)
• Boolean Literals: True, False
• Special Literal: None

Escape Characters

• Special characters represented by a backslash (\):
  • \\ (Backslash)
  • \' (Single quote)
  • \" (Double quote)
  • \n (Newline)
  • \t (Tab)
  • \uXXXX (Unicode character)

String Types

• Single Line: Ends on the same line (e.g., "Hello")
• Multiline:
  • With Backslash: """Hello \ World"""
  • Triple Quotes: """Hello \n World"""

Numeric Literals

• Integer: Can be decimal, octal (prefix 0o), or hexadecimal (prefix 0x).
• Floating Point: Can be fractional or in exponential notation.

Type Conversion

• Implicit Conversion: Done automatically by Python (e.g., int to float)
• Explicit Conversion: Using functions like int(), float(), str(), bool()

Input and Output

• Input: Use input() (returns string).
• Conversion Needed: Convert input to appropriate type (int(), float()).
• Output: Use print() with optional sep and end parameters to format output.

Operators

• Unary: +, -, ~, not
• Binary:
  • Arithmetic: +, -, *, /, %, **, //
  • Bitwise: &, |, ^, <<, >>
  • Relational: <, >, <=, >=, ==, !=
  • Logical: and, or, not
  • Assignment: =, +=, -=, *=, /=, //=, **=
  • Membership: in, not in
  • Identity: is, is not

Variables

• Definition: Created by assignment (e.g., x = 10)
• Dynamic Typing: Can change type (e.g., x = 100 then x = "text")

Expressions vs. Statements

• Expression: Produces a value (e.g., 5 + 3)
• Statement: Performs an action (e.g., print("Hello"))

Comments

• Single Line: # comment
• Multiline: """ comment """ or ''' comment '''

Functions

• Definition: Use def keyword to define (e.g., def my_function():)

Blocks and Indentation

• Block: Group of statements with consistent indentation.

Multiple Assignments

• Single Value: a = b = c = 10
• Multiple Values: x, y, z = 1, 2, 3

Common Errors

• Type Mismatch: Ensure correct types when performing operations or conversions.

Practical Exercises

• Basic Programs: Calculate area, convert units, process input, etc.

Special Cases and Cautions

• Dynamic Typing Caution: Ensure correct type operations to avoid errors.