← Teacher guide Markdown for Prepare

Models by hand: cheat sheet

Machine learning with Gradio · In any playground, open Reference to copy these.

running total

Start the total at 0 once, then add to it on every pass.

total = 0
while total < 10:
    total += int(input("Add: "))

variable

Give a value a name, so you can reuse and change it.

size = 50
Example
length = 120
forward(length)
left(90)
forward(length / 2)
What it draws
length = 120, then half of it

list

Keep many values in order under one name. The first item is place 0.

colours = ["red", "blue", "green"]

for each item

Work through a list, one item at a time.

for c in colours:
    pass
Example
pensize(6)
for c in ["red", "blue", "green"]:
    pencolor(c)
    forward(40)
What it draws
One line per colour in the list

print

Show text or a value in the output box.

print("Hello")

random number

Pick a random whole number between two values.

import random

n = random.randint(1, 10)

join text

Join pieces of text into one with +. Spaces only appear where they are inside the quotes.

"Hello, " + name

str

Turn a number into text, so it can be joined: "Score: " + str(score).

str(score)

dictionary value

The value stored under that key. The key goes in quotes. Assign to it to change it: star["speed"] = 8.

star["speed"]

read a file

Opens the file to read and gives you all of it as one piece of text.

with open("save.txt") as f:
    text = f.read()

test a model

Shuffle, then keep some examples back. Train on one part; test only on the other.

random.seed(1)
random.shuffle(penguins)
train = penguins[:250]
test = penguins[250:]

if / else

Do one thing or the other, depending on a condition.

if x > 0:
    pass
else:
    pass
Example
for x in [-90, -30, 30, 90]:
    penup()
    goto(x, 0)
    if x > 0:
        dot(30, "red")
    else:
        dot(30, "blue")
hideturtle()
What it draws
Red when x > 0, else blue

grow value

Change a value every pass: read the old one, store a new one.

size = 5
for i in range(20):
    forward(size)
    right(90)
    size = size + 5
Example
size = 5
for i in range(30):
    forward(size)
    right(90)
    size = size + 5
What it draws
The same spiral, grown by an update

def (function)

Name a group of steps, then run it by calling its name.

def shape():
    pass

shape()
Example
def zigzag():
    left(45)
    forward(30)
    right(90)
    forward(30)
    left(45)

zigzag()
zigzag()
zigzag()
What it draws
Defined once, called three times

dictionary

Values stored under names (keys). One dictionary can hold everything about one thing.

star = {"speed": 5, "points": 1}

in

True if the item is in the list (or the key is in the dictionary, or the letters are in the text).

if item in bag:
    pass

read a CSV

Each row of the file becomes a dictionary, keyed by the column names in the first line. Every value is text.

import csv

with open("music.csv") as f:
    rows = list(csv.DictReader(f))