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# Pick from a list
micro:bit Foundations · Lists
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## Today
**We are learning to** pick an item from a list at random, so it works however long the list grows.
- I can pick a random item from a list.
- I can say why the range is 0 to length − 1.
- I can add items to a list without changing the random part.
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## Why it matters
> A magic 8-ball, a game that deals a random card, a playlist on shuffle: each picks a place at random, then takes the item at that place.
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💬 Discussion
## Predict
**You shake this magic 8-ball twice. Can it give the same answer both times?**
- It always says Yes
- No: it never repeats until every answer has been used
- Yes: each shake picks a new random place, and it can be the same one
- No: it goes in order, Yes, then No, then Maybe
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✍️ Activity
## Roll a dice (3 min)
Roll a real dice twice. Can it give the same number both times?
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✅ Check
## What happened?
* Yes. Each shake picks a random place from 0 to 2, with no memory of the last one, so the same place can come up twice.
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✍️ Activity
## Run it
Open the lesson at this step and try it together.
[studio.learningwaypoints.com/tutorials/code/microbit/microbit-pick/?full=step-2#step-2](https://studio.learningwaypoints.com/tutorials/code/microbit/microbit-pick/?full=step-2#step-2)
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💬 Discussion
## Investigate
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✅ Check
## Which places?
**The list has 3 answers. Which places can pick random 0 to length − 1 choose?**
- Only 0
- 0, 1 or 2
- 1, 2 or 3
- 0, 1, 2 or 3
* Answer: 0, 1 or 2
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✅ Check
## Kai's 8-ball
Kai's program:
**Kai's magic 8-ball never says Yes, and sometimes shows nothing at all. Why?**
- pick random is broken
- The list needs four items
- Places start at 0, but Kai picks from 1 to 3: he skips Yes and asks for a place that is not there
- Yes is too short to show
* Answer: Places start at 0, but Kai picks from 1 to 3: he skips Yes and asks for a place that is not there
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✅ Check
## Ana's longer list
**Ana added two answers, so the list has five. Her code still picks from 0 to 2. What happens?**
- The two new answers never come up
- Only the new answers come up
- All five come up
- It shows an error
* Answer: The two new answers never come up
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✍️ Activity
## Draw a card (3 min)
Three cards numbered 0, 1 and 2 go in a hat. A student draws one, reads the item at that place, and puts it back.
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✍️ Activity
## Modify
- **Every answer:** Fix Ana's 8-ball with **length of list**, so all five answers can come up. Shake to check.
- **How many?:** Make **A** show how many answers are in the list.
[Open this step](https://studio.learningwaypoints.com/tutorials/code/microbit/microbit-pick/?full=step-4#step-4)
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💬 Discussion
## Investigate: Mix it up
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✅ Check
## Mix it up
**This is last lesson's mood chooser. choice starts at 0. You press A four times. Which mood shows after the 4th press?**
- Happy
- Hungry
- Nothing
- Tired
* Answer: Tired
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✍️ Activity
## Make
Make **rock, paper, scissors**. Each shake shows Rock, Paper or Scissors, picked at random from a list. Play against a friend with their own micro:bit (or the simulator).
[Open this step](https://studio.learningwaypoints.com/tutorials/code/microbit/microbit-pick/?full=step-6#step-6)
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✍️ Activity
## Change a team picker
This picks a name at random from a class list. Put in names from your class, then make **B** show how many names there are.
[Open this step](https://studio.learningwaypoints.com/tutorials/code/microbit/microbit-pick/?full=step-7#step-7)
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✍️ Activity
## Play a round (3 min)
Play rock, paper, scissors against the next pair: both shake at once.
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✅ Check
## Exit ticket
**A list has 6 items. What should pick random choose between, and why?**
* 0 and 5 (0 to length − 1), because places start at 0, so the last of 6 items is at place 5.