--- title: "Guess the number" subtitle: "Console bridge: text in, text out · Keep asking · Lesson 8" --- # Guess the number **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** Real programs are longer than a few lines. The skill is to find the part that does a job, then change just that part. :::teacher-note **In one sentence:** Students read a guessing game made of moves they know, find the part that does each job, change one part, and build a dice game from the same pieces. **Students should be able to say:** I can point to the lines that do each job in a longer program. I can change one part of a program without breaking the rest. I can build a new loop from parts I know. **Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Predict Read the program, one part at a time. How many tries will it say? ```python secret = 7 guess = input("Guess a number from 1 to 20: ") tries = 1 while guess != str(secret): if guess.isdigit() == False: print("Type a whole number.") elif int(guess) < secret: print("Too low.") else: print("Too high.") guess = input("Try again: ") tries += 1 print("Got it in " + str(tries) + " tries!") ``` :::keep-together **The secret is 7. You type 10, then 3, then 7. What number does the last line show?** My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** 3. tries starts at 1. The wrong guess 10 is followed by one more try, so tries is 2, then the wrong guess 3 makes it 3. 7 is right, so the loop ends and the program shows Got it in 3 tries! ::: ## Run Run the program in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Investigate ```python import random secret = random.randint(1, 20) guess = input("Guess a number from 1 to 20: ") tries = 1 while guess != str(secret): if guess.isdigit() == False: print("Type a whole number.") elif int(guess) < secret: print("Too low.") else: print("Too high.") guess = input("Try again: ") tries += 1 print("Got it in " + str(tries) + " tries!") ``` :::keep-together ### Find the parts **Match each part of the program with its job.** A. keeps asking until the guess is the secret B. counts every guess C. tells the player the guess was too low D. the computer picks a secret number {{columns 60% 40%}} {{rows 1}} | Part | Letter | |---|---| | `secret = random.randint(1, 20)` | | | `while guess != str(secret):` | | | `elif int(guess) < secret:` | | | `tries += 1` | | ::: :::teacher-note **Answer:** secret = random.randint(1, 20) → D. the computer picks a secret number; while guess != str(secret): → A. keeps asking until the guess is the secret; elif int(guess) < secret: → C. tells the player the guess was too low; tries += 1 → B. counts every guess The loop is the engine: it repeats the check, the hint, the new question and the count until the guess is right. ::: :::keep-together ### Spot the bug **With this version the program always says Got it in 2 tries, however many guesses it took. Click the wrong line.** ``` 1 secret = 7 2 guess = input("Guess a number from 1 to 20: ") 3 tries = 1 4 while guess != str(secret): 5 if guess.isdigit() == False: 6 print("Type a whole number.") 7 elif int(guess) < secret: 8 print("Too low.") 9 else: 10 print("Too high.") 11 guess = input("Try again: ") 12 tries += 1 13 print("Got it in " + str(tries) + " tries!") ``` Line: {{field-15}} Why is it wrong? {{lines-2}} ::: :::teacher-note **Answer:** line 12 tries += 1 is not indented, so it runs once after the loop, not on every guess. Indent it so it runs on every pass. ::: :::typical ## Modify Change the game one step at a time. Run after each change. **A bigger range.** Pick the secret from 1 to 100. **Only five tries.** Stop after five wrong guesses and show the secret. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. **A bigger range:** ```python import random secret = random.randint(1, 100) guess = input("Guess a number from 1 to 100: ") tries = 1 while guess != str(secret): if guess.isdigit() == False: print("Type a whole number.") elif int(guess) < secret: print("Too low.") else: print("Too high.") guess = input("Try again: ") tries += 1 print("Got it in " + str(tries) + " tries!") ``` **Only five tries:** ```python import random secret = random.randint(1, 20) guess = input("Guess a number from 1 to 20: ") tries = 1 while guess != str(secret) and tries < 5: if guess.isdigit() == False: print("Type a whole number.") elif int(guess) < secret: print("Too low.") else: print("Too high.") guess = input("Try again: ") tries += 1 if guess == str(secret): print("Got it in " + str(tries) + " tries!") else: print("Out of tries. The secret was " + str(secret) + ".") ``` ::: ::: ## Make Make a dice game with the same parts. The computer rolls a dice (a random number from 1 to 6) again and again until it gets a six, then prints how many rolls it took. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. ```python import random roll = random.randint(1, 6) count = 1 while roll != 6: roll = random.randint(1, 6) count += 1 print("It took " + str(count) + " rolls to get a six.") ``` ::: ## Exit ticket :::keep-together **Which line in the guessing game makes it ask again, and which line counts the guesses?** {{lines-3}} ::: :::teacher-note **Answer:** guess = input("Try again: ") asks again, and tries += 1 counts. :::