Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Lists/TuplesExample•Write a program to keep track of all students’ scores on exam 1.•Need a list of everyone’s score•Use 14 doubles•What about next semester?Lists•Ordered set of valuesscores=[90.5, 73, 87]•Each value accessed by using [ ] and indexscores[1] #would be 73•A list can contain different types -- including other listsscores=[90.5, 73, 87, “Mickey”, [67, 89]]•A list can be emptyscores=[]Examplescores=[90.5, 73, 87]90.573 87scores:Subscripts•Subscript describes which box of the array you are dealing with•List of size N has subscripts –0, 1, 2, … (n-1)–list of size 3 – 0, 1, 2•Subscript can be a variable or expression which produces an integer–scores[i]–scores[i+5]•If subscript specified does not exist – runtime errorRange•Lists of consecutive integers common•Use range() to generate–range(5) #0, 1, 2, 3, 4–range(1,5) #1, 2, 3, 4–range(1, 10, 2) #1, 3, 5, 7, 9Accessing List Elements•Print all elements of the list scores–Use only one print statementAccessing List Elements•Print all elements of the list scores–Use only one print statementscores = [90.5, 73, 82]i=0while(i<3):print scores[i]i = i+1Accessing List Elements•Using 3 as length is error pronescores = [90.5, 73, 82]i=0while(i<len(scores)):print scores[i]i = i+1Accessing List Elements•Another method -- short cut•Membershipscores[90.5, 73, 82]if 100 in scores:print “There is a perfect score!”scores = [90.5, 73, 82]for i in scores:print iOperators -- A lot like strings•Concatenationfirst_scores=[90,56,87]second_scores=[67,100,89]all_scores = first_scores+second_scores•Slicesall_scores[2:4] #yields [87,67] more_scores=all_scores[:] #makes a copy of all_scoresMutability•Lists are mutable - they can be changedscores[90.5, 73, 82]scores[1] = 100 #scores is now [90.5, 100, 82]•Lists can grow - using append function–append takes 1 argumentscores.append(12)scores.append([56, 78, 34])•Lists can shrink - using del function–del takes an element or slicedel scores[2]del scores[1:3]•Other functions - sort, reverseAliasing•Reference assignmentscores=[90.5, 73, 82]new_scores = scoresscores[0] = 100 #new_scores[0] changesscoresnew_scores90.5 73 82Cloningscores=[90.5, 73, 82]new_scores = scores[:]scores[0] = 100 #new_scores[0] DOES NOT changescoresnew_scores90.5 73 8290.5 73 82Exercises1. Use the interpreter to help you determine the outcome of each of the following statements. Why are the invalid statements invalid?list1 = [1,2,3]list2 = list1print list2list2 = list1[2]print list2list2.append(8)print list2list2 = list1list2.append(8)print list2list1[9] = "hello"print list2list1[2] = "hello"print list2Exercises1. Implement a program that prompts the user for a series of strings (using “quit” to end input) and stores them in a list. Then, for every string in the list, display it for the user and ask if he/she would like to delete it. Delete the appropriate strings and display the final list for the user.List Elements as Parameters•Write a function to add two elements of a listList Elements as Parameters•Write a function to add two elements of a list–How is the function called?def adder(num1, num2):return (num1 + num2)List Elements as Parameters•Write a function to add two elements of a list–How is the function called?adder(scores[0], scores[1])Passing Lists•Would like to pass an entire list into a function–Sum all elements, prompt user for valuesExamplesum(scores)def sum(list):sum = 0for i in list:sum += ireturn sumNested Listsexam_scores=[[90, 67, 34], [46, 99, 87], [89,78,67],[87,87,85]]#could represent three scores for four students •Access second score of third studentNested Listsexam_scores=[[90, 67, 34], [46, 99, 87], [89,78,67],[87,87,85]]#could represent three scores for four students •Access second score of third studentexam_scores[2][2]90 67 3446 99 8789 78 6787 87 8501230 1 2Exercises1. Implement a function that takes as input a list of integers and adds 5 to every element.2. Implement a program that prints all elements in a matrix.Tuples•Very similar to lists, but immutable–You can copy, but you cannot modify (append, del, assign new values)•Typically enclosed in ( )scores=(90.5, 73, 87)•An integer - scores = (70)•A tuple of one element - scores = (70,)•Convert a list to a tuple tuple_scores = tuple(list_scores)•Convert a tuple to a list - list_scores = list(tuple_scores)Swapping•Typical swap requires a temp variabletmp = bb = aa = tmp•Tuple assignmenta, b = b, ax, y, z = 4, 6, 8Return Valuesdef getnums() :n1 = input(“Enter number 1:”)n2 = input(“Enter number 2:”)return n1, n2x, y = getnums()print x #prints first number entered print y #prints second number enteredExercises1. Can you think of a way to write a function that takes as input a tuple of integers, adds 5 to every element, and returns a
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