Cheat Sheet: Programming from First Principles

Module 1

marks = [10, 20]
student = {"id": 1, "name": "Asha"}

• int, float, bool, str
• list, tuple, set, dict

Module 2

list(map(lambda x: x * 2, [1, 2, 3]))

• higher-order function = takes or returns a function
• map transforms, filter selects

Module 3

if score >= 40:
    result = "Pass"

• indentation defines blocks
• use comprehensions for compact collection building

Module 4

def gen():
    yield 1

• generators produce values on demand
• yield pauses and resumes

Module 5

double = lambda x: x + 1

• lambda calculus explains functions and application

Module 6

def make_adder(n):
    return lambda x: x + n

• closures remember outer values

Module 7

def add(x: int, y: int) -> int:
    return x + y

• Python is dynamic by default
• type hints help humans and tools

Module 8

from typing import TypeVar
T = TypeVar("T")

• inference is mostly tool-based in Python

Module 9

from dataclasses import dataclass

• class, @dataclass, Enum

Module 10

• concrete = exact type
• generic = still has a type variable

Module 11

def f(n):
    if n == 0:
        return 1
    return n * f(n - 1)

• recursion needs a base case

Module 12

• syntax = form
• semantics = behavior
• reduction = step-by-step evaluation

Module 13

from typing import Protocol

• duck typing, Protocol, ABC

Module 14

T = TypeVar("T")

• polymorphism = one design, many types