## Practice Problems for Module 04 # Part 1 - Warm up questions intro_list = [1,2,3,-4,-5,"six", "7", True] # Ensure that you understand the lists created by the following list slices. #intro_list[2:4] #intro_list[4:10] #intro_list[3:4] #intro_list[3:3] #intro_list[10:4] #intro_list[:3] #intro_list[4:] #intro_list[1:10:2] #intro_list[2:6:-1] #intro_list[6:2:-1] #intro_list[::-1] # Ensure you understand the following list subscripting #intro_list[0] #intro_list[5] #intro_list[10] #intro_list[-1] #intro_list[-4] #intro_list[-20] # Write a Pyhton function find_multiples that consumes values, a list of integers, # and m, a positive integer, and returns a list containing all multiples of m in values. # For example, # find_multiples([1,2,3,4,5,6], 7) => [] # find_multiples([1,2,3,4,5,6], 2) => [2,4,6] def find_multiples(values, m): pass ## Mutating list: Answer the questions posed in the code below. L = [1,2,3] L.append('a') # What is value of L? M = L # M & L are aliases. Why? M.extend([True, False]) # What is the value of L? M? L.insert(3,"new") # What is the value of L? M? L = [] # What is the value of L? M? Are they aliases? M.append(1) # What is the value of M? M.remove(1) # What is the value of M? x = M.pop(1) # What is value of x? M? ## Solve the following using built-in list operations (no recursion needed). P = [1,2,1,3,1,4,2,3,4] # Verify that P contains 3 occurrences of 1. # Write three statements to find the indices of these three occurrences of 1 in P # using the index function. # How could you check if there is a fourth occurrence of 1 in P using the results # of the step above, slicing, and in? Don't use count here. # Use abstract list functions and lambda to write the following two function: # # Write a Python function find_As that consumes grades, a list of natural numbers # between 0 and 100, and returns the list of values in grades greater or # equal to 80. # e.g. find_As([87,45,90,80,67,75,100]) => [87.90,80,100] def find_As(grades): pass # Use abstract list functions and lambda to write the following function: # Write a Python function keep_last that consumes a list of nonempty strings, # and returns the list containing only the last characters in each string. # e.g. keep_last(["abc", "abba", "hit"]) => ['c','a','t'] def keep_last(words): pass # Write a Python function, clear_all, that consumes a vals, a list of integers, # and uses recursion to mutate the list to contain all zeroes. # The function returns None. # Be sure to include the full design recipe for clear_all. def clear_all(vals): pass # Part 2 - Extra Practice # Problem 1 ## Part a ## Builds on a quesion in Module 03 practice ## Write a function new_names that consumes two lists - one of people's ## current full names, and a second, parallel list, of their new last names. The ## function returns a new list containing all the updated names. ## For example, update_names(["Abigail Melissa Smith", "Hao Chan", ## "Timothy Howe"], ["Jones", "Chan", "Howe-Williams"]) => ## ["Abigail Melissa Jones", "Hao Chan", "Timothy Howe-Williams"] ## ## Part b ## Rewrite new_names using abstract list functions. # Problem 2 ## Part a ## Write a recursive function count_A_grades which consumes a ## list of numbers in the range [0:100] and returns the number ## of values from the list in the range [80:100]. ## ## Part b ## Rewrite count_A_grades using abstract list functions. # Problem 3 ## Write the function strange_change, which consumes vals, a non-empty list of numbers, and ## sets a value in the list to 100, based on the value of the first ## element in the list. If vals[0] a valid index (i.e. between 0 and len(vals)-1), the value ## stored at pos vals[0] is set to 100. If vals[0] < 0, then the first value ## in the list is set to 100. If vals[0) >= len(lst), then the value ## at the last list position is set to 100. The function returns the ## index of the changed value. ## For example, ## L = [3,2,3,5,8,0] ## strange_change(L) => 3, and modifies L to [3,2,3,100,8,0] ## L = [-2,2,4,9] ## strange_change(L) => 0, and modifies L to [100,2,4,9] ## L = [90,3] ## strange_change(L) => 1, and modifies L to [90,100]. # Problem 4 ## Builds on a quesion in Module 03 practice ## Write a function change_titles which consumes a list of names, ## and modifies that list so that all names with titles "Miss" and "Mrs." ## are changed to include the title "Ms." instead. # Problem 5 ## Part a ## Write a recursive function count_in_range which consumes a ## list of integers, numbers, and two other integers, lo and hi, ## and returns the number of values v in numbers ## that satisfy lo <= v <= hi. ## ## Part b ## Rewrite using abstract list functions # Problem 6: ## Write a Python function get_positives that consumes nothing, and returns ## a list of positive integers entered by the user at the keyboard while the ## function is running. The functon asks the user to enter an integer. If a positive ## value is entered, it is appended to the list created so far. If 0 is entered, ## the program continues but 0 is not added to the list. If a negative value ## is entered, the function terminates. # Problem 7: ## Part a ## Write a function add_numbers that consumes a list containing any number of ## values of any type, and returns the sum of the numeric values (int or float) ## in the list. The result should be produced as a floating point value. ## For example, ## * add_numbers([1,2,3.4,4,5]) => 15.4 ## * add_numbers(['a', True]) => 0 ## ## Part b ## Rewrite using abstract list functions # Problem 8 ## Write a function list_mod that consumes a list of natural numbers, counts, and a positive ## natural number, n, and mutates the list so that each entry in counts, say k, is ## changed to k mod n (remainder). The function returns None. # Problem 9 ## Write a function modify that consumes a list of values, info, and ## changes all entries in the list containing strings to contain 0 instead. ## The function returns the number of changed values.