Overview
This lecture covered the foundational concepts of Python programming, focusing on character sets, tokens, variables, assignments, operators, input/output functions, and the structure of a Python program.
Introduction to Python Fundamentals
- Python is a high-level programming language with simple syntax and dynamic typing.
- Basics include interactive/script modes, character sets, tokens, and program structure.
Character Sets in Python
- The character set includes all valid characters Python can recognize (letters, digits, special symbols, spaces).
- Supports ASCII and Unicode characters (A-Z, a-z, 0-9, special symbols, white spaces).
Tokens in Python
- Tokens are the smallest units in a Python program, essential for syntax and structure.
- Five types of tokens: keywords, identifiers, literals, operators, punctuators.
Keywords
- Keywords are reserved words with special, predefined meanings (e.g., if, else, for, while, True, False, None).
- Cannot be used as identifiers (variable or function names).
Identifiers
- Identifiers are names given to variables, functions, classes, etc.
- Must start with a letter or underscore, can contain letters, digits, underscores, and cannot use special symbols or keywords.
Literals
- Literals are fixed values used directly in code (e.g., numbers, strings, boolean values).
- Types include string literals (in quotes), numeric literals (integers, floats), boolean literals (True/False), special literal (None), collections (list, tuple, dictionary).
Operators
- Operators perform operations on variables and values (e.g., +, -, *, /, //, %, **).
- Categories: arithmetic, bitwise, comparison, logical, assignment, membership, identity.***
Punctuators
- Punctuators are symbols that structure code (e.g., (), [], {}, :, ,, ;, @, #, quotes).
Structure of a Python Program (Bare Bones)
- A program consists of expressions, statements, comments, indentation, and functions.
- Indentation defines code blocks (four spaces or a tab).
- Functions are reusable code blocks defined with
def.
Variables and Assignment
- Variables are references (labels) to stored values in memory.
- Assignment uses
= with variable name on the left and value on the right.
- Supports multiple and dynamic assignments (type can change at runtime).
Input and Output Functions
- Input with
input() function (always returns a string; convert to int/float as needed).
- Output with
print() function (supports separators and end character).
- Common escape sequences:
\n (new line), \t (tab).
Key Terms & Definitions
- Token — Smallest individual unit in a Python program.
- Keyword — Reserved word with predefined meaning, not usable as identifiers.
- Identifier — Name given to a variable, function, class, etc.
- Literal — Fixed value written directly in code.
- Operator — Symbol that performs operations on data.
- Punctuator — Symbol used to structure Python code.
- Variable — Named reference to a value stored in memory.
- Assignment — Process of storing a value in a variable using
=.
- Indentation — Leading spaces or tabs that define code blocks.
- Function — Reusable block of code defined with
def.
Action Items / Next Steps
- Practice writing Python programs using variables, input/output, and operators.
- Review and memorize common keywords and token types.
- Read Chapter 4 for practice-based questions.
- Experiment with assignment, indentation, and block structures in code.