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marp: true
theme: default
html: true
---
# A menu that keeps showing
Console bridge: text in, text out · Menus and testing
---
## Today
**We are learning to** put a menu inside while True, choose with if and elif, and leave the loop with break when the person picks quit.
- I can use while True with break to make a menu that keeps showing.
- I can add a choice to a menu with elif.
- I can build my own small menu app.
---
## Why it matters
> Ticket machines, ATMs and the settings on a phone are all menus: show the choices, wait for one, do it, and show the menu again.
---
💬 Discussion
## Predict
```python
total = 0
while True:
choice = input("1 add $5, 2 pay: ")
if choice == "1":
total += 5
print("Total: $" + str(total))
elif choice == "2":
print("Pay $" + str(total))
break
else:
print("Please choose 1 or 2.")
print("Thank you")
```
**You type 1, 1, 3, then 2. What does the program show?**
- Total: $5, Total: $10, Please choose 1 or 2., Pay $10, Thank you
- Total: $5, Total: $10, Please choose 1 or 2., and then the program stops
- It never stops, even after 2
- Total: $5, Total: $10, Please choose 1 or 2., Pay $10, and then it asks again
---
✍️ Activity
## Run it
{{embed: https://studio.learningwaypoints.com/tutorials/_playground/index.html?code=total+%3D+0%0Awhile+True%3A%0A++++choice+%3D+input%28%221+add+%245%2C+2+pay%3A+%22%29%0A++++if+choice+%3D%3D+%221%22%3A%0A++++++++total+%2B%3D+5%0A++++++++print%28%22Total%3A+%24%22+%2B+str%28total%29%29%0A++++elif+choice+%3D%3D+%222%22%3A%0A++++++++print%28%22Pay+%24%22+%2B+str%28total%29%29%0A++++++++break%0A++++else%3A%0A++++++++print%28%22Please+choose+1+or+2.%22%29%0Aprint%28%22Thank+you%22%29%0A}}
_If it does not load:_ [open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/code/console/console-menu/?full=step-2#step-2)
---
✅ Check
## What happened?
* Total: $5, Total: $10, Please choose 1 or 2., Pay $10, Thank you. break leaves the whole loop at once, not just the if, so the program carries on after the loop and ends.
---
💬 Discussion
## Investigate
```python
total = 0
while True:
choice = input("1 add $5, 2 pay: ")
if choice == "1":
total += 5
print("Total: $" + str(total))
elif choice == "2":
print("Pay $" + str(total))
break
else:
print("Please choose 1 or 2.")
print("Thank you")
```
---
✅ Check
## Follow a session
```python
total = 0
while True:
choice = input("1 add $5, 2 pay: ")
if choice == "1":
total += 5
print("Total: $" + str(total))
elif choice == "2":
print("Pay $" + str(total))
break
else:
print("Please choose 1 or 2.")
print("Thank you")
```
**You type 1, 1, 3, 2. Fill in the total after each choice and whether the loop goes round again.**
| choice | total after | loop goes round again |
|---|---|---|
| 1 | 5 | yes |
| 1 | ? | ? |
| 3 | ? | ? |
| 2 | ? | ? |
* Answer: 10, yes, 10, yes, 10, no
---
✅ Check
## Spot the bug
**Choosing 2 shows Pay $10, but then the menu comes back and the program never ends. Click the line where something is missing.**
```
1 total = 0
2 while True:
3 choice = input("1 add $5, 2 pay: ")
4 if choice == "1":
5 total += 5
6 elif choice == "2":
7 print("Pay $" + str(total))
8 else:
9 print("Please choose 1 or 2.")
10 print("Thank you")
```
* Answer: line 7
---
✅ Check
## What does break do?
```python
total = 0
while True:
choice = input("1 add $5, 2 pay: ")
if choice == "1":
total += 5
print("Total: $" + str(total))
elif choice == "2":
print("Pay $" + str(total))
break
else:
print("Please choose 1 or 2.")
print("Thank you")
```
**What does break do when it runs inside an if inside a while True?**
- Stops the program
- Leaves only the if
- Skips to the next pass
- Leaves the whole loop at once
* Answer: Leaves the whole loop at once
---
✍️ Activity
## Modify
Add a drink for $2 as choice 3. Paying becomes choice 4. Update the menu text too.
---
✍️ Activity
## Live: Modify
{{embed: https://studio.learningwaypoints.com/tutorials/_playground/index.html?code=total+%3D+0%0Awhile+True%3A%0A++++choice+%3D+input%28%221+add+%245%2C+2+pay%3A+%22%29%0A++++if+choice+%3D%3D+%221%22%3A%0A++++++++total+%2B%3D+5%0A++++++++print%28%22Total%3A+%24%22+%2B+str%28total%29%29%0A++++elif+choice+%3D%3D+%222%22%3A%0A++++++++print%28%22Pay+%24%22+%2B+str%28total%29%29%0A++++++++break%0A++++else%3A%0A++++++++print%28%22Please+choose+1+or+2.%22%29%0Aprint%28%22Thank+you%22%29%0A}}
_If it does not load:_ [open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/code/console/console-menu/?full=step-4#step-4)
---
💬 Discussion
## Investigate: Mix it up
```python
total = 0
while True:
choice = input("1 add $5, 2 pay: ")
if choice == "1":
total += 5
print("Total: $" + str(total))
elif choice == "2":
print("Pay $" + str(total))
break
else:
print("Please choose 1 or 2.")
print("Thank you")
```
---
✅ Check
## Mix it up
```python
total = 0
while True:
choice = input("1 add $5, 2 pay: ")
if choice == "1":
total += 5
print("Total: $" + str(total))
elif choice == "2":
print("Pay $" + str(total))
break
else:
print("Please choose 1 or 2.")
print("Thank you")
```
**You type 3, 3, 2. How many times does the menu question appear?**
* Answer: 3
---
✍️ Activity
## Make
Make your own menu app: a café, a game shop, a quiz scoreboard or a unit converter. It needs `while True`, at least three choices, a reply for a wrong choice, and a way to quit.
---
✍️ Activity
## Live: Make
{{embed: https://studio.learningwaypoints.com/tutorials/_playground/index.html?code=%23+Menu+app%3A+while+True%2C+at+least+three+choices%2C+a+reply+for+a+wrong+choice%2C+and+a+way+to+quit.%0A}}
_If it does not load:_ [open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/code/console/console-menu/?full=step-6#step-6)
---
✍️ Activity
## Order from my menu (4 min)
Swap seats and use your partner's menu app. Try every choice and a wrong one.
---
✅ Check
## Exit ticket
**What does break do, and what happens to the program after it?**
* break leaves the loop at once. The program carries on with the first line after the loop.