## Practice Problems 5 Complete before class on 2021-10-15

Complete the following problems on paper. Try to solve each problem on paper first before using Thonny to confirm your answers.

1. [PP Problem 8.4] The value of the variable ids is the list [4353, 2314, 2956, 3382, 9362, 3900]. Using list methods, do the following:

a. Remove 3382 from the list.
b. Get the index of 9362.
c. Insert 4499 in the list after 9362.
d. Extend the list by adding [5566, 1830] to it.
e. Reverse the list.
f. Sort the list.

2. Since strings and lists are both sequences, many Python expressions can be applied to both string values and list values. For each of the expressions below, determine whether the expressions is valid if value is both a string and a list, only for a string, only for a list or if it depends.

1. value + value
2. [value]
3. len(value)
4. value[:4]
5. "abc" + value
3. What is the value of x after this code executes?

 x = []
for i in range(3):
x.insert(0, len(x))

4. Write docstrings for the following functions describing what each of them do:

1. Mystery Function 1

def mystery1(num1, num2):
result = []
for i in range(num1):
result.append(num2)
return result

2. Mystery Function 2

def mystery2(num1, num2):
return [num2]*num1

3. Mystery Function 3

def mystery3(a_list):
for i in range(len(a_list) // 2):
other_index = len(a_list)-i-1
temp = a_list[i]
a_list[i] = a_list[other_index]
a_list[other_index] = temp

5. [PP Problem 8.7] Write a function named same_first_last that takes a list as a parameter and returns True if and only if the first and last element of the list are equal. You can assume that the list has at least one element.

6. [PP Section 8.8] You are experimenting with the following code to provide a list of colors in sorted order, but you are getting an error when your for loop executes. What is the problem and how would you fix it?

 colors = 'red orange yellow green blue purple'.split()
sorted_colors = colors.sort()
for color in sorted_colors:
print(color)

7. I typically teach two classes a semester. At the beginning of the semester I want to find out how many students are enrolled in both classes. Assume that I have two files containing the respective class rosters. Write a function named common_students that takes the two files as arguments and returns the number of students enrolled in both courses. Recall that you can use the in operator to test if a value is present in a list.