Intro to Python Programming

Key idea

A variable is a labeled box: you put a value in it once, then use its name anywhere you want that value. Text goes in quotation marks (a string); numbers do not. With an f-string you can drop a variable straight into a sentence, so a program can greet a player by name instead of saying the same thing every time.

Vocabulary

variable

A named box that stores a value so you can use it again later.

assign

To put a value into a variable using the = sign.

integer

A whole number with no decimal point, like 10.

f-string

A sentence that starts with f, where anything inside { } is filled in from a variable.

Plan your code

Project: About Me Generator. Write, step by step, what your program should do.

Debugging question

This should print My name is Alex, but it prints the word name instead. The variable's value is not getting filled in. What has to go around name inside an f-string?

name = "Alex"
print(f"My name is name.")

Write the fix:

Reflection

You changed what the program says just by changing one variable. Why is that better than typing the player's name over and over in every line?

Key idea

input() is how a program listens. It shows a prompt, then stops and waits for the player to type and press Enter. Their answer gets stored in a variable, so the program can use it - their name, their guess, their choice - in what it does next. Keep in mind: input() always gives back text.

Vocabulary

input()

A Python command that asks a question and waits for the user to type an answer.

prompt

The message input() shows to tell the user what to type.

user

The person using the program - in a game, the player.

Plan your code

Project: Mini Chatbot. Write, step by step, what your program should do.

Debugging question

Running this causes an error before the question even shows up. The message inside input() is text for the user to read. What does every piece of text need around it?

name = input(What should I call you? )

Write the fix:

Reflection

Last week your program always said the same thing. Now it answers you. What could you ask a player at the start of a game to make it feel like it is about them?

Key idea

A conditional lets the program choose. Python checks a condition - something that is either true or false - and runs the indented lines under it only if the condition is true. With if, elif, and else, a program can react one way to a right answer, another to a close answer, and another to a wrong one. That is how a game decides whether you scored, won, or lost.

Vocabulary

condition

A question with a true or false answer, like answer == "Earth".

if

Runs the indented lines below it only when its condition is true.

elif

Checks another condition when the ones above it were false.

else

Runs when none of the conditions above it were true.

==

Checks whether two values are equal (different from =, which stores a value).

Plan your code

Project: Trivia or Personality Quiz. Write, step by step, what your program should do.

Debugging question

Python shows an error on the if line. One equals sign stores a value in a variable. What do you use when you want to check whether two things are the same?

answer = input("Which planet do we live on? ")
if answer = "Earth":
    print("Correct!")

Write the fix:

Reflection

Your program now reacts differently to different answers. In your final game, what is one decision the program will need to make, and what should happen for each choice?

Key idea

A loop repeats code so you do not have to write it a hundred times. A while loop keeps going as long as its condition is true - perfect for a game that should keep asking until the player wins. Something inside the loop has to eventually make the condition false, or it runs forever. Since input() gives text, we use int() to turn the guess into a number we can compare.

Vocabulary

loop

Code that repeats instead of running once.

while

Repeats the lines below it as long as its condition stays true.

int()

Turns typed text like "7" into the number 7 so you can compare it.

infinite loop

A loop that never stops because its condition never becomes false.

Plan your code

Project: Guess the Number Game. Write, step by step, what your program should do.

Debugging question

This game never ends, even when the player types 7. The secret is the number 7, but input() gives back the text "7". Why are they not equal, and what turns text into a number?

secret = 7
guess = 0
while guess != secret:
    guess = input("Guess a number from 1 to 10: ")

Write the fix:

Reflection

A loop let you ask again and again without repeating yourself. What part of your final game might need to repeat - the turns, the questions, the rounds?

Key idea

A function is a reusable recipe. You write the steps once after def and give it a name; after that, you run all those steps just by calling the name. A parameter lets you hand the function different information each time, so one greet function can welcome any player. Writing a function does not run it; calling it does.

Vocabulary

function

A named block of code you can run again and again by calling its name.

def

The keyword that creates a new function.

parameter

An input a function takes, listed inside its parentheses.

call

To run a function by writing its name with parentheses, like greet("Alex").

Plan your code

Project: Game Helper Functions. Write, step by step, what your program should do.

Debugging question

This stops with an error about a missing argument. The greet function asks for a player in its parentheses. Look at the last line - what did the call forget to give it?

def greet(player):
    print(f"Welcome, {player}!")

greet()

Write the fix:

Reflection

You wrote show_score once and used it twice. In your final game, what is something you will do more than once that could become a function?

Key idea

A list holds many values in one variable, written inside square brackets. random.choice() reaches into a list and pulls out one item at random, so the program can surprise the player. To use random you first bring it in with import random at the top - the first time you have needed a tool that is not built in. Lists plus randomness are what make a game feel different every time you play.

Vocabulary

list

An ordered collection of values inside square brackets, like ["a", "b", "c"].

item

One value stored in a list.

import

Brings in extra tools Python does not load by default, like the random module.

random.choice()

Picks one item from a list at random.

Plan your code

Project: Random Adventure Game. Write, step by step, what your program should do.

Debugging question

Python says random is not defined. This program uses random.choice(), but random is a tool that has to be brought in first. What single line belongs at the very top?

paths = ["a dark forest", "a quiet cave"]
path = random.choice(paths)
print(path)

Write the fix:

Reflection

Two players run this and get different stories. Why does that make a game more fun to play more than once?

Key idea

Real programs are built from small pieces you already know, added one at a time. Start with a plan and a skeleton that runs, then add one feature, test it, and only then add the next. A small game that works is a real win - more than a big one that never runs.

Vocabulary

plan

A short outline of what a program should do, written before you code it.

skeleton

A small working program you start from and build onto.

test

Running your program with different inputs to see whether it works.

bug

A mistake in code that makes the program do the wrong thing.

Plan your code

Project: Build Your Own Python Mini Game. Write, step by step, what your program should do.

Debugging question

Python points at the while line with a syntax error. Every line that starts a block - if, while, def - ends with the same small symbol. Look at the end of that line.

secret = random.choice([1, 2, 3])
guess = 0
while guess != secret
    guess = int(input("Pick a number: "))

Write the fix:

Reflection

You built a game out of the eight ideas from this program. Which week's idea did you lean on the most, and why?