lab06.pdf - lab06 November 26, 2020 1 Lab 6: Randomization...

lab06
November 26, 2020
1 Lab 6: Randomization
Welcome to Lab 1 of Data 8.2x!
We will go over iteration and simulations , as well as introduce the concept of randomness .
First, set up the tests and imports by running the cell below.
[1]: import numpy as np
from datascience import *
import otter
grader = otter . Notebook()
1.1 1. Nachos and Conditionals
In Python, Boolean values can either be True or False . We get Boolean values when using
comparison operators such as < (less than), > (greater than), and == (equal to). A list of common
comparison operators can be found below!
[2]: 3 > 1 + 1
[2]: True
We can even assign the result of a comparison operation to a variable.
[3]: result = 10 / 2 == 5
result
[3]: True
Arrays are compatible with comparison operators. The output is an array of boolean values.
[4]: make_array( 1 , 5 , 7 , 8 , 3 , -1 ) > 3
[4]: array([False, True, True, True, False, False])
Waiting on the dining table just for you is a hot bowl of nachos! Let’s say that whenever you take
a nacho, it will have cheese, salsa, both, or neither (just a plain tortilla chip).
1

Using the function call np.random.choice(array_name) , let’s simulate taking nachos from the
bowl at random. Start by running the cell below several times, and observe how the results change.
Question 1.1 Assume we took ten nachos at random, and stored the results in an array called
ten_nachos as done below. Find the number of nachos with only cheese using code (do not hardcode
the answer).
Hint: Our solution involves a comparison operator and the np.count_nonzero method.
[6]: ten_nachos = make_array( 'neither' , 'cheese' , 'both' , 'both' , 'cheese' , 'salsa' , ␣
, →
'both' , 'neither' , 'cheese' , 'both' )
number_cheese = np . count_nonzero(ten_nachos == 'cheese' )
number_cheese
[6]: 3
[7]: grader . check( "q1_1" )
[7]:
All tests passed!
Conditional Statements
A conditional statement is made up of many lines that allow Python to choose from different
alternatives based on whether some condition is true.
Here is a basic example.
def sign(x):
if x > 0:
return 'Positive'
How the function works is if the input x is greater than 0 , we get the string 'Positive' back.
If we want to test multiple conditions at once, we use the following general format.
if <if expression>:
<if body>
elif <elif expression 0>:
<elif body 0>
elif <elif expression 1>:
<elif body 1>
...
else:
<else body>
2

Only one of the bodies will ever be executed. Each if and elif expression is evaluated and
considered in order, starting at the top. As soon as a true value is found, the corresponding body
is executed, and the rest of the expression is skipped. If none of the if or elif expressions are
true, then the else body is executed. For more examples and explanation, refer to