Python Syntax Guide

Fundamentals Deep Dive

Python Syntax: Readable, strict, and predictable

Master the whitespace-sensitive syntax that differentiates Python from brace-heavy languages. Learn the token types, statement boundaries, and formatting conventions that make codebases consistent.

Practice indentationReview keywords

The whitespace contract

• Python uses indentation to define code blocks. Four spaces is the community standard (enforced by Black).
• Mixing tabs and spaces raises TabError. Configure your editor to insert spaces automatically.
• Continuation lines inside parentheses, brackets, or braces don't require trailing backslashes.

result = (
    user.first_name.title()
    + " "
    + user.last_name.title()
)

Statements & expressions

Concept	Description
Simple statement	Fits on one logical line (x = 3, print("hi")).
Compound statement	Includes a header + indented block (e.g., if, for, with).
Expression	Anything that returns a value (literals, function calls, comprehensions).

Know when to reach for colons (:) – they always terminate the header of compound statements.

Keywords you can't use as identifiers

Python keywords (3.12)

Keyword	Purpose
def	Define a function
class	Define a class
if / elif / else	Conditional branching
for / while	Loops
try / except / finally	Error handling
match / case	Structural pattern matching
import / from	Module loading
with	Context managers
lambda	Anonymous functions
yield	Generator control

Keywords are reserved; do not use them as variable or function names.

Comments and docstrings

• Single-line comment: # explain why
• Block comments: stack multiple single-line comments
• Docstrings: triple quotes directly under a definition

def fetch_user(user_id: str) -> dict:
    """Retrieve a user profile from the API."""
    ...

Structural patterns to master

Conditional blocks

if balance <= 0:
    raise ValueError("Overdrawn")
elif balance < 100:
    print("Low funds")
else:
    print("All good")

Pattern matching (3.10+)

match payload:
    case {"type": "user", "id": user_id}:
        handle_user(user_id)
    case {"type": "order", "id": order_id}:
        handle_order(order_id)
    case _:
        log.warning("Unknown payload")

Linting + formatting

• Use Black for formatting (88 character lines).
• Use Ruff or Flake8 to catch unused imports, shadowed variables, etc.
• Add an .editorconfig to enforce indentation and newline rules across editors.

Next up in your learning path

Deep dive into indentation rules

Eliminate TabErrors and keep blocks readable.

Syntax

Explore control flow

Put syntax into action with branching and loops.

Next pillar

Study the keywords set

Memorize reserved words and their semantics.

Reference

Frequently Asked Questions

Do I need semicolons in Python?

Semicolons are optional and only useful when chaining multiple short statements on one line. Prefer one statement per line for readability.

How do I continue a long statement?

Wrap the statement in parentheses, brackets, or braces. Python automatically continues lines inside those delimiters without requiring `\`.

What is the best way to comment code?

Explain intent—not mechanics. Use docstrings for modules/classes/functions. Keep comments short and update them when logic changes.