slides-06-02.qmd

---
title: "random (slides)"
format: revealjs
slide-number: true
df-print: kable
---

# CSC 110 -- Generating Random Numbers and Other Important Functions and Methods

## Announcement

* Check gradescope for grades
* Lecture next Friday, Oct 11 will be on Zoom.
  * You can also come here and watch the recording so that TAs can help
  * Attendance window will be 9am - 9pm 

## random module

We need to `import` the module `random`

What do the functions `.random()` and `.randint()` return?

```{python}
#| echo: true
import random

n = random.random() #returns a random float between 0 and 1
print(n)

n = random.randint(0, 9) #returns a random integer betweem 0 and 9.


print(n)
```

## Write a function

1. Function name is `pick_winner`
1. It takes a list as argument
1. It generates a random index, and returns the item at that position

```{python}
#| eval: false
#| echo: true
winner = pick_winner(["Peter", "Joan", "Mary", "June"])
print(winner)
```

## Write a function -- solution

```{python}
#| eval: true
#| echo: true
import random

def pick_winner(names):
  index = random.randint(0, len(names) - 1)
  return names[index]

if __name__ == "__main__":
  winner = pick_winner(["Peter", "Joan", "Mary", "June"])
  print(winner)
```

## Setting a seed 

What happens when you run `pick_winner` multiple times?

To get always the same result (for autograding purposes, for example) we can set a seed.

```{python}
#| eval: true
#| echo: true
import random

def pick_winner(names):
  random.seed(123)
  index = random.randint(0, len(names) - 1)
  return names[index]

if __name__ == "__main__":
  winner = pick_winner(["Peter", "Joan", "Mary", "June"])
  print(winner)
```


## Write a function

Write a function `random_list` that takes as argument a list of `numbers`. Iterate over each list element (with a `while` loop), replacing each integer with a random number between zero and the original number. Set the seed as `123` in your function.

Name your file `random_list.py` and submit to Gradescope.

```{python}
#| eval: false
#| echo: true
# test case
assert random_list([3, 2, 1, 3, 5]) == [0, 1, 0, 3, 2]
```

## Write a function -- solution

```{python}
#| eval: true
#| echo: true
import random

def random_list(numbers):
  random.seed(123)
  index = 0
  while index < len(numbers):
    item = numbers[index]
    numbers[index] = random.randint(0, item)
    index += 1
  return numbers

if __name__ == "__main__":
  assert random_list([3, 2, 1, 3, 5]) == [0, 1, 0, 3, 2]
  print("pass the test")
```