Example 1: #

print("Input x")
text = input("> ")
x = int(text)
print("x + 4 =", x + 4)

Write the code in IDLE
We need to save it before we can run it.
That means we care about local files and directories.
This is a plain text file.
- We can open it in Windows Notepad
- A program like Microsoft Word won’t work.
We can run it by:
- Clicking “run” in the run menu.
- Pressing F5.
- Opening up a command line window and running it with the python command.
A Python program is a series of statements (think “commands”)
The Python interpreter (a program called “python”) executes the program in such a way that it looks like the statements run in order.

Flow control #

print("Input x")
x = 10
while x > 0:
    text = input("> ")
    x = int(text)
    if x % 2 == 0:
        print("x + 4 =", x + 4)

Data types: #

Numbers: int, float
Strings
Collections: list, tuple, dict, set

Functions #

def add2(xx):
    return xx + 2

We spent most of the semester designing functions, but writing code has the same basic problem as writing prose: It’s hard to know where to start.

So this semester we used a design recipe:

Purpose statement
Signature (e.g. int -> int)
Tests
Stub
Standard pattern
Write the body

Design with lists #

Insertion sort:

# [number] -> [number]
def sort(xs):
    ys = []
    
    for x in xs:
        ys = insert(ys, x)

    return ys

# We need a helper

# [number], number -> [number]
def insert(xs, y):
    lt = []
    gt = []
   
    for x in xs:
        if x <= y:
            lt.append(x)
        elif x > y:
            gt.append(x)
    
    return lt + [y] + gt

Design with Dictionaries #

Design a method that takes a list of numbers and returns a list of how many times the number in that position appeared in the lsit.

Example: [7, 7, 1, 7, 2, 2, 7, 1, 3] -> [4, 4, 2, 4, 2, 2, 4, 2, 1]

version 1: nested loop
version 2: two loops and a dictionary

How many times through a loop in each case?

Directory Trees and Recursion #

from pathlib import Path

def search(path):
    for item in path.iterdir():
        if item.is_dir():
            search(item)
        else:
            print(item)

wd = Path.cwd()
search(wd)

Web Scraping #

Vault example
Show latest versions

ConsList / Binary Trees #

Recursive data

AI, Word Game #

Generating pictures was fun.
The Intermediate Programing are done, so now it’s time to beat them. The highest real name on the leaderboard is Job Bonestoppel…