MAT 215 Chapters 5

Which of the following statements is false? a. List method remove deletes the first element with a specified value—a NameError occurs if remove's argument is not in the list b. List method count searches for its argument in a list and returns the number of times it is found. c. List method reverse reverses the contents of a list in place. d. List method copy returns a new list containing a shallow copy of the original list.

Answer: a. Actually, a ValueError occurs if remove's argument is not in the list

Which of the following statements is false? a. Reductions process a sequence's elements into a small number of values. b. The built-in functions len, sum, min and max perform reductions. c. You also can create custom reductions using the functools module's reduce function. d. In the worlds of big data and Hadoop, MapReduce programming is based on the filter, map and reduce operations in functional-style programming.

Answer: a. Actually, reductions process a sequence's elements into a single value.

Consider a two-dimensional list with three rows and four columns (i.e., a 3-by-4 list) that might represent the grades of three students who each took four exams in a course: a = [[77, 68, 86, 73], [96, 87, 89, 81], [70, 90, 86, 81]] Which of the following statements a), b) or c) is false? a. Writing the list as follows makes its row and column tabular structure clearer: a = [77, 68, 86, 73], # first student's grades [96, 87, 89, 81], # second student's grades [70, 90, 86, 81] # third student's grades b. The element names in the last column all have 3 as the second index. c. The following nested for statement outputs the rows of the two-dimensional list a one row at a time: for row in a: for item in row: print(item, end=' ') print() d. All of the above statements are true.

Answer: a. Actually, writing the list as follows makes its row and column tabular structure clearer: a = [[77, 68, 86, 73], # first student's grades [96, 87, 89, 81], # second student's grades [70, 90, 86, 81]] # third student's grad

Which of the following statements a), b) or c) is false? a. Lists can contain other lists as elements. b. To identify a particular table element, we specify two indices—by convention, the first identifies theelement's column, the second the element's row. c. Multidimensional lists can have more than two indices. d. All of the above statements are true.

Answer: b. Actually, by convention the first index identifies the element's row and the second indexidentifies the element's column.

Which of the following statements is false? .a. A common functional-style programming operation is filtering elements to select only those that matcha condition. b. Filtering typically produces a list with more elements than the data being filtered. c. To do filtering in a list comprehension, use the if clause. d The following list comprehension includes in list4 only the even values produced by the for clause:list4 = [item for item in range(1, 11) if item % 2 == 0]

Answer: b. Actually, filtering typically produces a list with fewer elements than the data being filtered.

Which of the following statements a), b) or c) is false? a. A list comprehension's expression can perform tasks, such as calculations, that map elements to new values (possibly of different types). b. Mapping is a common functional-style programming operation that produces a result with more elements than the original data being mapped. c. The following list comprehension uses the expression item ** 3 to map each value in a range to the value's cube: list3 = [item ** 3 for item in range(1, 6)] d. All of the above statements are true.

Answer: b. Actually, mapping is a common functional-style programming operation that producesa result with the same number of elements as the original data being mapped.

Which of the following statements a), b) or c) is false? a. Sometimes you'll need to find the minimum and maximum of more complex objects, such as strings. b. Consider the following comparison: 'Red' < 'orange' The letter 'R' "comes after" 'o' in the alphabet, so 'Red' is greater than 'orange' and the condition above is False. c. Built-in function ord returns the numerical value of a character. d. All of the above statements are true.

Answer: b. Actually, strings are compared by their characters' underlying numerical values, and lowercase letters have higher numerical values than uppercase letters, so the condition is True

Which of the following statements is false? a. The following code uses built-in function map with a lambda to square each value in numbers: list(map(lambda x: x ** 2, numbers)) b. Function map's first argument is a function that receives one value and returns a new value—in Part (a), a lambda that squares its argument. Function map's second argument is an iterable of values to map. c. Function map uses eager evaluation. d. The equivalent list comprehension to Part (a) is: [item ** 2 for item in numbers]

Answer: c. Actually, function map, like filter, returns an iterator so map uses lazy evaluation.

Which of the following statements a), b) or c) is false? a. Visualizations help you "get to know" your data. b. Visualizations give you a powerful way to understand data that goes beyond simply looking at raw data. c. The Matplotlib visualization library is built over the Seaborn visualization library and simplifies many Seaborn operations. d. All of the above statements are true.

Answer: c. Actually, the Seaborn visualization library is built over the Matplotlib visualization library and simplifies many Matplotlib operations

Which of the following statements a), b) or c) is false? a. In a call to list method index, specifying the starting and ending indices (as the second and thirdarguments) causes index to search from the starting index up to but not including the ending indexlocation. b. The call: numbers.index(5, 7)is equivalent to: numbers.index(5, 7, len(numbers)) c. The following looks for the value 7 in the range of elements with indices 0 through 4:numbers.index(7, 0, 4) d. All of the above statements are true.

Answer: c. Actually, the code looks for 7 in the range of elements with indices 0 through 3

Which of the following statements is false? a. You can slice sequences to create new sequences of the same type containing subsets of the original elements. b. Slice operations can modify mutable sequences. Slice operations that do not modify a sequence work identically for lists, tuples and strings. c. The following code creates a slice consisting of the elements at indices 2 through 6 of the list numbers:numbers = [2, 3, 5, 7, 11, 13, 17, 19]numbers2 = numbers[2:6] d. When taking a slice of a list, the original list is not modified.

Answer: c. Actually, the slice consists of the elements at indices 2 through 5 of the

5.11 Q1: Which of the following statements is false? a. Python does not have a built-in stack type, but you can think of a stack as a constrained list. b. You push using list method append, which adds a new element to the end of the list. c. You pop using list method pop with no arguments, which removes and returns the item at the front ofthe list. d. You can run out of memory if you keep pushing items faster than you pop them.

Answer: c. Actually, you pop using list method pop with no arguments, which removes and returnsthe item at the end of the list.

. Consider the list color_names:color_names = ['orange', 'yellow', 'green']Which of the following statements a), b) or c) is false? a. Lists also have methods that add and remove elements. b. Method insert adds a new item at a specified index. The following inserts 'red' at index 0:color_names.insert(0, 'red') c. You can add a new item to the end of a list with method append. d. All of the above statements are true.

Answer: d.

Which of the following statements a), b) or c) is false? a. A generator expression is similar to a list comprehension, but is enclosed in parentheses (rather than[]) and creates an iterable generator object that produces values on demand. b. The generator expression in the following for statement squares and returns only the odd values in numbers: numbers = [10, 3, 7, 1, 9, 4, 2, 8, 5, 6] for value in (x ** 2 for x in numbers if x % 2 != 0): print(value, end=' ') c. A generator expression does not create a list. d. All of the above statements are true.

Answer: d.

Which of the following statements is false? a. For simple functions that return only a single expression's value, you can use a lambda expression to define the function inline where it's needed—typically as it's passed to another function. b. A lambda expression is an anonymous function—that is, a function without a name. c. In the following filter call the first argument is the lambda: filter(lambda x: x % 2 != 0, numbers) d. A lambda explicitly returns its expression's value.

Answer: d. Actually, a lambda implicitly returns its expression's value—there is no return statement in a lambda

Which of the following statements is false? a. The following code uses built-in function filter to obtain the odd values in numbers: = [10, 3, 7, 1, 9, 4, 2, 8, 5, 6] def is_odd(x) :"""Returns True only if x is odd.""" return x % 2 != 0 list(filter(is_odd, numbers)) b. Python functions are objects that you can assign to variables, pass to other functions and return fromfunctions. c. Function filter's first argument must be a function that receives one argument and returns True ifthe value should be included in the result. d. Function filter returns an iterator, so filter's results are produced immediately.

Answer: d. Actually, because function filter returns an iterator, filter's results are not produced until you iterate through them—this is an example of lazy evaluation

: Which of the following statements is false? a. The built-in function any returns True if any item in its iterable argument is True .b. The built-in function all returns True if all items in its iterable argument are True. c. Non-empty iterable objects also evaluate to True, whereas any empty iterable evaluates to False. d. Functions any and all are examples of external iteration in functional-style programming.

Answer: d. Actually, functions any and all are additional examples of internal iteration in functional-style programming.

Which of the following statements a), b) or c) is false? a. You can use *= to multiply a sequence—that is, append a sequence to itself multiple times. b. After the following snippet, the list numbers contains two copies of the original list's contents: numbers *= 2 c. The following code searches the list numbers for the value 5 starting from index 7 and continuing through the end of the list :numbers.index(5, 7) d. All of the above statements are true.

Answer: d..

Which of the following statements is false?] a. Usually, you iterate over a tuple's elements. b. Like list indices, tuple indices start at 0. c. The following snippets create a time_tuple representing an hour, minute and second, display the tuple, then use its elements to calculate the number of seconds since midnight: In [1]: time_tuple = (9, 16, 1) In [2]: time_tupleOut[2]: (9, 16, 1) In [3]: time_tuple[0] * 3600 + time_tuple[1] * 60 + time_tuple[2] Out[3]: 33361 d. Assigning a value to a tuple element causes a TypeError

a. Actually, though a tuple is a sequence, usually you do not iterate over a tuple's elements;rather, you access each individually. Usually, you iterate over a list's elements.

Which of the following statements is false? a. You can use del with a list to remove the element at any valid index or the element(s) from any validslice. b. The following code creates a list, then uses del to remove its last element: numbers = list(range(0, 10)) del numbers[1] c. The following deletes the list's first two elements: del numbers[0:2] d. The following uses a step in the slice to delete every other element from the entire list: del numbers[::2]

b. Actually, Part (b)'s del statement should be del numbers[-1] or del numbers[9]

Which of the following statements is false? a. The += augmented assignment statement can be used with strings and tuples, even though they'reimmutable. b. In the following snippets, after the two assignments, tuple 1 and tuple 2 are two different copies of the same tuple object: In [1]: tuple1 = (10, 20, 30) In [2]: tuple2 = tuple1 In [3]: tuple2Out[3]: (10, 20, 30) c. Concatenating the tuple (40, 50) to tuple1 from Part (b), as in tuple1 += (40, 50) creates a new tuple, then assigns a reference to it to the variable tuple1—tuple 2 still refers to the original tuple. d. For a string or tuple, the item to the right of += must be a string or tuple, respectively—mixing types causes a Type Error.

b. Actually, after the two assignments, tuple1 and tuple2 refer to the same tuple object

Which of the following statements is false? a. The following code deletes only the first three elements of numbers by assigning an empty list to thethree-element slice: numbers[0:3] = [] b. The following code assigns a list's elements to a slice of every other element of numbers: numbers = [2, 3, 5, 7, 11, 13, 17, 19] numbers[2:2:2] = [100, 100, 100, 100] c. The following code deletes all the elements in numbers, leaving the existing list empty: numbers[:] = [] d. When you assign a new object to a variable the original object that the variable referenced will begarbage collected if no other variables refer to it

b. Actually, numbers[2:2:2] s. b. numbers[::2]. The code as written in Part (b) yields aValueError.5.6 del Statement

Which of the following statements a), b) or c) is false? a. You can use list method sort as follows to arrange a list's elements in ascending order: numbers = [10, 3, 7, 1, 9, 4, 2, 8, 5, 6] numbers.sort() b. To sort a list in descending order, call list method sort with the optional keyword argumentreverse=False. c. Built-in function sorted returns a new list containing the sorted elements of its argument sequence—the original sequence is unmodified. d. All of the above statements are true.

b. Actually, to sort a list in descending order, call list method sort with the key word argument reverse=True—with reverse=False, sort actually sorts in ascending order.

Which of the following statements is false? a. Tuples are immutable. b. Tuples must store heterogeneous data (that is, data of different types). c. A tuple's length is its number of elements. d. A tuple's length cannot change during program execution

b. Actually, tuples can store heterogeneous data, but the data also can be homogeneous(that is, data of the same type)

: a. We've replaced the results of the four list comparisons in snippets [4] through [7] below with???. What are those four values? In [1]: a = [1, 2, 3] In [2]: b = [1, 2, 3] In [3]: c = [1, 2, 3, 4] In [4]: a == bOut[4]: ??? In [5]: a == cOut[5]: ??? In [6]: a < cOut[6]: ??? In [7]: c >= bOut[7]: ??? a. False, True, False, False .b. True, False, False, True. c. True, False, True, True. d. True, True, True, False.

c

Which of the following statements is false? a. Often, you'll want to determine whether a sequence (such as a list, tuple or string) contains a value thatmatches a particular key value. b. Searching is the process of locating a key in a sequence. c. List method index takes as an argument a search key—the value to locate in the list—then searchesthrough the list from index 1 and returns the index of the first element that matches the search key. d. List method index raises a ValueError if the value you're searching for is not in the list.

c. Actually, list method index searches from index 0

Which of the following statements is false? a. When you specify a slice and omit the starting index, 0 is assumed. So, the slice numbers[:6] isequivalent to the slice numbers[0:6]. If you omit the ending index, Python assumes the sequence'slength. b. Omitting both the start and end indices on a slice copies the entire sequence .c. Slices make deep copies of the sequence's elements. d. With slices, the new sequence's elements refer to the same objects as the original sequence's elements,rather than to separate copies.

c. Actually, though slices create new objects, slices make shallow copies of the originalsequence's elements—that is, they copy the elements' references but not the objects they refer to

Which of the following statements is false? a. Lists are mutable—their elements can be modified. b. You can insert and delete list elements, changing the list's length. c. You can get the individual characters in a string, and you can assign a new value to one of the string's characters. d. Python's string and tuple sequences are immutable—they cannot be modified.

c. Actually, you can get the individual characters in a string, but you cannot assign a new value to one of the string's characters—attempting to do so causes a TypeError. Strings are immutable.

Consider the list c:c = [-45, 6, 0, 72, 1543] Which of the following statements a), b) or c) is false? a. You reference a list element by writing the list's name followed by the element's index (that is, itsposition number) enclosed in square brackets ([], known as the subscription operator). b. The names of c's elements are c[0], c[1], c[2], c[3] and c[4]. c. The length of c is 5. d. All of the above statements are true.

d

Which of the following statements a), b) or c) is false? a. List comprehensions provide a concise and convenient notation for creating new lists. b. List comprehensions can replace many for statements that iterate over existing sequences and create new lists, such as: list1 = [] for item in range(1, 6): list1.append(item) We can accomplish the same task in a single line of code with a list comprehension: list2 = [item for item in range(1, 6)] c. The list comprehension's for clause in Part (b) iterates over the sequence produced by range(1, 6).For each item, the list comprehension evaluates the expression to the left of the for clause and places the expression's value (in this case, the item itself) in the new list .d. All of the above statements are true

d

Which of the following statements a), b) or c) is false? a. The following code creates a student_tuple with a first name, last name and list of grades:student_tuple = ('Amanda', 'Blue', [98, 75, 87]) b. Even though the tuple in Part (a) is immutable, its list element is mutable. c. In the expression student_tuple[2][1], Python views student_tuple[2] as the element of the tuple containing the list [98, 75, 87], then uses [1] to access the list element containing 75. d. All of the above statements are true

d

Which of the following statements a), b) or c) is false? a. The preferred mechanism for accessing an element's index and value is the built-in function enumerate,which receives an iterable and creates an iterator that, for each element, returns a tuple containing theelement's index and value. b. The following code uses the built-in function list to create a list of tuples containing enumerate'sresults:colors = ['red', 'orange', 'yellow']colors_list = list(enumerate(colors)) c. The following for loop unpacks each tuple returned by enumerate into the variables index and valueand displays them:for index, value in enumerate(colors):print(f'{index}: {value}') d. All of the above statements are true.

d

Which of the following statements a), b) or c) is false? a. You can concatenate two lists, two tuples or two strings using the + operator. The result is a new sequence of the same type containing the left operand's elements followed by the right operand's elements. b. A TypeError occurs if the + operator's operands are different sequence types—for example,concatenating a list and a tuple is an error. c. List elements can be accessed via their indices and the subscription operator ([]). d. All of the above statements are true

d

Which of the following statements a), b) or c) is false? a. You can unpack any sequence's elements by assigning the sequence to a comma-separated list of variables. b. A ValueError occurs if the number of variables to the left of the assignment symbol is not identical to the number of elements in the sequence on the right .c. The following code unpacks a sequence produced by range:number1, number2, number3 = range(3) d. All of the above statements are true

d

Which of the following statements a), b) or c) is false? a. You can use a negative step to select slices in reverse order. b. The following code creates a new list in reverse order:numbers[::-1] c. You can modify a list by assigning to a slice of it—the rest of the list is unchanged. d. All of the above statements are true

d

Which of the following statements is false? a. Collections are prepackaged data structures consisting of related data items. b. Examples of collections include your favorite songs on your smartphone, your contacts list, a library's books, your cards in a card game, your favorite sports team's players, the stocks in an investment portfolio,patients in a cancer study and a shopping list. c. Lists are modifiable and tuples are not. Each can hold items of the same or different types. d. Tuples can dynamically resize as necessary, growing and shrinking at execution time

d

Which of the following statements is false? a. You can pack a tuple by separating its values with commas .b. When you output a tuple, Python always displays its contents in parentheses. c. You may surround a tuple's comma-separated list of values with optional parentheses. d. The following statement creates a one-element tuple:a_singleton_tuple = ('red')

d. Actually, ('red') simply creates a string variable, whereas ('red',) with a comma included creates a one-element tuple

Which of the following statements is false? a. The following code deletes all of the list's elements: del numbers[:] b. The del statement can delete any variable. c. The following code deletes the variable numbers from the interactive session: del numbers d. After deleting numbers from the interactive session, attempting to display it displays an empty list.

d. Actually, attempting to display numbers after it has been deleted from the session causes a NameError. The variable numbers is gone

Which of the following statements is false? a. The function modify_elements multiplies each element of its list argument by 2: def modify_elements(items): """"Multiplies all element values in items by 2.""" for i in range(len(items)): items[i] *= 2 b. Part (a)'s function modify_elements' items parameter receives a reference to the original list, so the statement in the loop's suite modifies each element in the original list object. c. When you pass a tuple to a function, attempting to modify the tuple's immutable elements results in aTypeError. d. Tuples may contain mutable objects, such as lists, but those objects cannot be modified when a tuple is passed to a function.

d. Actually, those objects still can be modified when a tuple is passed to a function

Which of the following statements a), b) or c) is false? a. The following code uses a list comprehension to create a list of 600 random die values, then uses NumPy's unique function to determine the unique roll values (guaranteed to include all six possible face values) and their frequencies: rolls = [random.randrange(1, 7) for i in range(600)] values, frequencies = np.unique(rolls, return_counts=True) b. The NumPy library provides the high-performance ndarray collection, which is typically much faster than lists. c. Specifying the keyword argument return_counts=True tells unique to count each unique value's number of occurrences. d. All of the above statements are true.

nswer: a. Actually, though it is most likely that the code snippet in Part (a) will create a list containing all six possible face values, the die rolling is random so it is not guaranteed