# Lesson 5. Loops in Python Exercise

## Learning Objectives

This page of exercises will test the skills that you learned in the previous lessons in this chapter. You will practice using loops to help with common coding tasks, using for and while loops, and looping over different types of data.

## Challenge 1: Print Numbers in a list

The list below contains temperature values for a location in Boulder, Colorado. Create a for loop that loops through each value in the list and prints the value like this: 

temp: 47

HINT: you can print a string and a variable together using the syntax:

print("temp:", variable_name_here)

# Data to convert to celsius

boulder_avg_high_temp_f = [
47,
49,
57,
64,
72,
83,
89,
87,
79,
67,
55,
47
]

boulder_avg_high_temp_f

[47, 49, 57, 64, 72, 83, 89, 87, 79, 67, 55, 47]

# Add your code here


temp: 47
temp: 49
temp: 57
temp: 64
temp: 72
temp: 83
temp: 89
temp: 87
temp: 79
temp: 67
temp: 55
temp: 47


## Challenge 2: Modify Numeric Values in a List

Below is a list of values that represents the average monthly high temperature in Boulder, CO., collected by NOAA. They are currently in Fahrenheit, but can be converted to Celsius by subtracting 32, and multiplying by 5/9.

celcius = (fahrenheit - 32) * 5/9


Create a new list with these same temperatures converted to Celsius using a for loop. Call your new list: boulder_avg_high_temp_c

HINT: to complete this challenge you may want to create a new empty list first. Then you can use list_name.append() in each loop iteration to add a new value to your list.

# Add your code here


[8.333333333333334,
9.444444444444445,
13.88888888888889,
17.77777777777778,
22.22222222222222,
28.333333333333336,
31.666666666666668,
30.555555555555557,
26.11111111111111,
19.444444444444446,
12.777777777777779,
8.333333333333334]


## Challenge 3: Round Values In a List

Create a loop that rounds the values in the list that you created above: boulder_avg_high_temp_c to only two decimal places.

To round your data, you can use the Python function round(). The first argument in the round() function is the number to round, and the second argument is the number of decimals you want after it’s been rounded. See how this works below.

c = 7.3848234
round(c, 2)

# 7.38


Create a new list called boulder_avg_high_temp_c_round that contains temperature data that has been rounded.

# Add your code here


[8.33,
9.44,
13.89,
17.78,
22.22,
28.33,
31.67,
30.56,
26.11,
19.44,
12.78,
8.33]


## Challenge 4: Print A List of Directories

The code below creates a list of directories called all_dirs. Create a for loop that prints each directory name.

import os
from glob import glob
import earthpy as et

out_path = et.data.get_data(url = file_url)

# Set working directory to earth-analytics
os.chdir(os.path.join(et.io.HOME,
"earth-analytics",
"data",

# Creating all_dirs list of directories to loop through

data_dirs = os.path.join(out_path, "*")
all_dirs = glob(data_dirs)


# Add your code here


/root/earth-analytics/data/earthpy-downloads/avg-monthly-temp-fahr/Sonoma


## Challenge 5: Print A List of All Files Within Each Directory

Above, you printed the name of each directory stored in a list of directories. Use the same for loop that you created above to print a list of all files in each directory.

HINT: you will want to use the glob function to create a list of files within each directory.

# Add your code here


['/root/earth-analytics/data/earthpy-downloads/avg-monthly-temp-fahr/Sonoma/Sonoma-2001-temp.csv', '/root/earth-analytics/data/earthpy-downloads/avg-monthly-temp-fahr/Sonoma/Sonoma-1999-temp.csv', '/root/earth-analytics/data/earthpy-downloads/avg-monthly-temp-fahr/Sonoma/Sonoma-2000-temp.csv', '/root/earth-analytics/data/earthpy-downloads/avg-monthly-temp-fahr/Sonoma/Sonoma-2002-temp.csv', '/root/earth-analytics/data/earthpy-downloads/avg-monthly-temp-fahr/Sonoma/Sonoma-2003-temp.csv']


## Bonus Challenge 1: Get Data from List of Files

Above, you created a list inside of a for loop to view all of the files stored in two separate folders. These files are csv files that can be opened with pandas as a DataFrame. The files contain the average monthly temperature for two different study locations, Sonoma and San Diego. Their are csv files for each location for the years between 1999 and 2003.

For this challenge, use nested for loops to get data from the files and find the average temperature in January over the years for the two sites. The end result should be two variables that represent the average January temperature for each site. Their are many ways to get this data, so don’t be afraid to get creative!

# You will need pandas for this challenge
import pandas as pd


San Diego January Mean Temperature from 1999 to 2003: 65.52 ºF
Sonoma January Mean Temperature from 1999 to 2003: 56.82 ºF


## Bonus Challenge 2: Collatz Conjecture

The Collatz Conjecture is a mathematic rule that says that if the following rules are performed on any positive interger, the number will eventually reach

1. The rules are:

2. If the integer is even, the next integer is one half of the current integer.
3. If the integer is odd, the next term is 3 times the current integer plus 1.

If these rules are followed, any integer will eventually reach one. Using a while loop, implement these rules so that a variable you enter into the while loop has these rules run on it until it equals one. Here are some helpful hints to help you implement these rules:

1. To check if a number is odd or even in Python, it is common practice to see if the remainder of the number divided by 2 equals zero. If you remember, % will get the remainder of a number divided by another number. So, to see if a number is even, the code n%2 == 0 will return True if n is even, and False if n is odd.
2. The while loop will run until the input number equals one. But you also need to remember not to run the code on the number if it does equal one. So in the odd calculation, make sure that the number doesn’t equal one before you run the calculation on it.

Print out the number variable with each pass through of the while loop. Have your number variable equal 10000 before the while loop is run. Careful with this, it shouldn’t take long to run. If it is taking a long time to run, there’s probably a mistake in your code and your while loop will be running forever until you stop it! Once your code runs, change the number variable to see it run on any number you want!

For further explanation on the Collatz Conjecture, and what it looks like to implement it, this YouTube video explains the basics of the math behind it and the Wikipedia page on the number has more in depth explanations of the math.

# Add your code here


10000
5000.0
2500.0
1250.0
625.0
1876.0
938.0
469.0
1408.0
704.0
352.0
176.0
88.0
44.0
22.0
11.0
34.0
17.0
52.0
26.0
13.0
40.0
20.0
10.0
5.0
16.0
8.0
4.0
2.0
1.0
`