MAT 215 Chapter 3

_______ is an informal English-like language for "thinking out" algorithms. a. Code b. Pseudocode c. Python d. Quasicode

b

Which of the following statements is false? a. A sentinel value indicates "end of data entry." b. Sentinel-controlled iteration is often called indefinite iteration because the number of iterations is not known before the loop begins executing. c. A sentinel value must match one acceptable input value. d. Grades on a quiz are typically nonnegative integers between 0 and 100, so the value -1 is an acceptable sentinel value for grades data.

c. Actually, a sentinel value must not be confused with any acceptable input value.

ython provides two iteration statements—________ and ________: a. do while and for b. while and for each c. do while and for each d. while and for

d

Which of the following statements is false? a. The argument of each of the statistics module's mean, median and mode functions must be an iterable. b. To help confirm the median and mode values of a grades list, you can use the built-in sorted function to get a copy of grades with its values arranged in increasing order, as in the following session, which makes it clear that both the median and the mode are 85: In [1]: grades = [85, 93, 45, 89, 85] In [2]: sorted(grades) Out[2]: [45, 85, 85, 89, 93] c. If a list's number of values is even, median returns the mode of the two middle values. d. The mode function causes a StatisticsError for lists like [85, 93, 45, 89, 85, 93] in which there are two or more "most frequent" values. Such a set of values is said to be bimodal.

. Actually, if a list's number of values is even, median returns the average (mean) of the two middle values.

Which of the following statements is false? a. You typically create a Decimal from a string. b. Decimals support the standard arithmetic operators +, -, *, /, //, ** and %, as well as the corresponding augmented assignments. c. You may perform arithmetic between Decimals and integers. d. You may perform arithmetic between Decimals and floating-point numbers.

Actually, you may not perform arithmetic between Decimals and floating-point numbers.

Various Python statements enable you to specify that the next statement to execute may be other than the next one in sequence. This is called ________ and is achieved with Python control statements. a. transfer of control b. alternate execution c. spread execution d. None of the above

a

With regard to the following code segment: # process 10 students for student in range(10): # get one exam result result = int(input('Enter result (1=pass, 2=fail): ')) if result == 1: passes = passes + 1 else: failures = failures + 1 which of the following statements is true? a. The if statement is nested in the for statement. b. The if statement follows the for statement in sequence. c. The for statement is nested in the if statement. d. None of the above.

a

Which of the following statements a), b) or c) is false? a. With a nonfatal logic error, an IPython interactive session terminates. b. For a fatal logic error in a script, an exception occurs (such as a ZeroDivisionError from an attempt to divide by 0), so Python displays a traceback, then terminates the script. c. A fatal error in interactive mode terminates only the current snippet. Then IPython waits for your next input. d. All of the above statements are true.

a. Actually, with a nonfatal logic error, the code executes, but produces incorrect results.

Which of the following statements is false? a. You place the not operator before a condition to choose a path of execution if the original condition (without the not operator) is True. b. The if statement if not grade == -1: print('The next grade is', grade) also can be written as follows: if grade != -1: print('The next grade is', grade) c. The Boolean not operator reverses the meaning of a condition—True becomes False and False becomes True. d. The not operator is a unary operator—it has only one operand.

a. Actually, you place the not operator before a condition to choose a path of execution if the original condition (without the not operator) is False.

Which of the following statements is false? a. Indenting a suite is required; otherwise, an IndentationError syntax error occurs. b. If you have more than one statement in a suite, those statements do not need to have the same indentation. c. Sometimes error messages may not be clear. The fact that Python calls attention to the line is often enough for you to figure out what's wrong. d. Programs that are not uniformly indented are hard to read.

b. Actually, an IndentationError occurs if you have more than one statement in a suite and those statements do not have the same indentation.

Which of the following statements is false? a. Built-in function print displays its argument(s), then moves the cursor to the next line. You can change this behavior with the argument end, as in print(character, end=' ') b. Python calls end a keyword argument, and end is a Python keyword. c. The end keyword argument is optional. If you do not include it, print uses a newline ('\n') by default. d. Keyword arguments are sometimes called named arguments.

b. Actually, end is not a Python keyword.

Which of the following statements is false? a. The while statement allows you to repeat one or more actions while a condition remains True. b. The following code sets product to the first power of 2 larger than 64: product = 2 while product < 64: product = product * 2 c. Something in a while statement's suite must ensure that the condition eventually becomes False. Otherwise, a logic error called an infinite loop occurs. d. In applications executed from a Terminal, Command Prompt or shell, type Ctrl + c or control + c (depending on your keyboard) to terminate an infinite loop.

b. Actually, the condition in the while statement must be product <= 64 or the code finds the first power of 2 which is 64 or larger.

Which of the following statements is false? a. The decision (diamond) symbol contains a condition that can be either True or False. b. The diamond flowchart symbol has three flowlines emerging from it. c. One flowline emerging from the diamond flowchart symbol indicates the direction to follow when the condition in the symbol is True. This points to the action (or group of actions) that should execute. d. Another flowline emerging from the diamond flowchart symbol indicates the direction to follow when the condition is False. This skips the action (or group of actions).

b. Actually, the diamond flowchart symbol has two flowlines emerging from it.

Which of the following statements is false? a. The descriptive statistics mean, median and mode are measures of central tendency—each is a way of producing a single value that is in some sense typical of the others. b. The following session creates a list called grades, then uses the built-in sum and len functions to calculate the median "by hand"—sum calculates the total of the grades (397) and len returns the number of grades (5): In [1]: grades = [85, 93, 45, 89, 85] In [2]: sum(grades) / len(grades) Out[2]: 79.4 c. Like functions min and max, sum and len are both examples of functional-style programming reductions—they reduce a collection of values to a single value. d. The Python Standard Library's statistics module provides functions for calculating the mean, median and mode—these, too, are reductions.

b. Actually, the session uses the built-in sum and len functions to calculate the mean "by hand."

he most important flowchart symbol is the ________, which indicates that a decision is to be made, such as in an if statement. a. rectangle b. flowline c. diamond d. small circle

c

Which of the following statements a), b) or c) is false? a. In an f-string, you can optionally follow a replacement-text expression with a colon (:) and a format specifier that describes how to format the replacement text. b. The format specifier .2f formats data as a floating-point number (f) with two digits to the right of the decimal point (.2). c. Formatting floating-point data with .2f rounds it to the tenths position. d. All of the above statements are true.

c. Actually, Formatting data with .2f rounds it to the hundredths position.

Which of the following statements is false. a. Experience has shown that the most challenging part of solving a problem on a computer is developing an algorithm for the solution. b. Once a correct algorithm has been specified, creating a working Python program from the algorithm is typically straightforward. c. A requirements statement describes how a program should operate but not what the program is supposed to do. d. Variables for totaling and counting normally are initialized to zero before they're used.

c. Actually, a requirements statement describes what a program is supposed to do, but not how the program should do it.

Which of the following statements is false? a. The following statement uses an f-string with two placeholders to format year and amount: print(f'{year:>2}{amount:>10.2f}') b. The placeholder {year:>2} uses the format specifier >2 to indicate that year's value should be right aligned (>) in a field of width 2—the field width specifies the number of character positions to use when displaying the value. c. For single-digit year values 1-9, the format specifier >2 displays a value followed by the space character, thus right aligning the years in the first column. d. The format specifier 10.2f in the placeholder {amount:>10.2f} formats amount as a floating-point number (f) right aligned (>) in a field width of 10 with a decimal point and two digits to the right of the decimal point (.2). Formatting a column of amounts this way aligns their decimal points vertically, as is typical with monetary amounts.

c. Actually, for single-digit year values 1-9, the format specifier >2 displays a space character followed by the value, thus right aligning the years in the first column.

Which of the following statements is false? a. Sometimes the suites in an if...else statement assign different values to a variable, based on a condition, as in: grade = 87 if grade >= 60: result = 'Passed' else: result = 'Failed' b. You can replace if...else statements like the one above using a concise conditional expression: result = ('Passed' if grade >= 60 else 'Failed') c. The parentheses in a conditional expression are required; otherwise, a syntax error occurs. d. All of the above statements are true.

c. Actually, the parentheses are not required, but they can make it clear that the statement in Part (b) assigns the conditional expression's value to result.

Which of the following statements a), b) or c) is false? a. Augmented assignments abbreviate assignment expressions in which the same variable name appears on the left and right of the assignment's =, as total does in: for number in [1, 2, 3, 4, 5]: total = total + number b. The following code re-implements the for statement in Part (a) using an addition augmented assignment (+=) statement: for number in [1, 2, 3, 4, 5]: total += number c. The statement f = f ** 3 may be replaced by the more concise augmented assignment statement f *= 3. d. All of the above statements are true.

c. Actually, the statement f = f ** 3 may be replaced by the more concise augmented assignment statement f **= 3.

Which of the following statements is false? a. Many scripts can be decomposed into initialization, processing and termination phases. b. The following statement creates the variable grades and initializes it with a list of 10 integer grades. grades = [98, 76, 71, 87, 83, 90, 57, 79, 82, 94] c. Iteration is called definite iteration if the number of iterations is first known after the loop finishes executing. d. The Style Guide for Python Code recommends placing a blank line above and below each control statement.

c. Actually, with definite iteration, the number of iterations is known before the loop begins executing.

What does the following for statement print? for counter in range(10): print(counter, end=' ') a. It doesn't run because it's syntactically incorrect. b. 0 1 2 3 4 5 6 7 8 9 10 c. 1 2 3 4 5 6 7 8 9 d. 0 1 2 3 4 5 6 7 8 9

d

What does the following line of code display? print(10, 20, 30, sep=', ') a. 102030 b. 10,20,30 c. 10 20 30 d. 10, 20, 30

d

Which of the following statements a), b) or c) is false? a. The Python Standard Library is divided into modules—groups of related capabilities. b. The decimal module defines type Decimal and its capabilities. c. To use Decimal, you must first import its module, as in import decimal and refer to the Decimal type as decimal.Decimal, or you must indicate a specific capability to import using from...import, as in: from decimal import Decimal which imports only the type Decimal from the decimal module so that you can use it in your code. d. All of the above statements are true.

d

Which of the following statements a), b) or c) is false? a. You can solve any computing problem by executing a series of actions in a specific order. b. An algorithm is a procedure for solving a problem in terms of the actions to execute, and the order in which these actions execute. c. Program control specifies the order in which statements (actions) execute in a program. d. All of the above statements are true.

d

Which of the following statements a), b) or c) is false? a. You form each Python program by combining as many control statements of each type as you need for the algorithm the program implements. b. With Single-entry/single-exit (one way in/one way out) control statements, the exit point of one connects to the entry point of the next. This is similar to the way a child stacks building blocks—hence, the term control-statement stacking. c. You can construct any Python program from only six different forms of control (sequential execution, and the if, if...else, if...elif...else, while and for statements). You combine these in only two ways (control-statement stacking and control-statement nesting). This is the essence of simplicity. d. All of the above statements are true.

d

Which of the following statements about the IPython session below is true? In [1]: gender = 'Female' In [2]: age = 70 In [3]: if gender == 'Female' and age >= 65: ...: print('Senior female') ...: Senior female a. The session defines two variables, then tests a condition that's True if and only if both simple conditions are True—if either (or both) of the simple conditions is False, the entire and expression is False. b. The right side of the and operator evaluates only if the left side is True. c. The combined condition can be made clearer by adding redundant (unnecessary) parentheses (gender == 'Female') and (age >= 65) d. All of the above statements are true.

d

Which of the following statements is false? a. Any expression may be evaluated as True or False. b. A condition which evaluates to a nonzero value is considered to be True, and a condition which evaluates to a value of zero is considered to be False. c. Strings containing characters are True and empty strings ('', "" or """""") are False. d. All of the above statements are true.

d

Which of the following statements is false? a. The sequence to the right of the for statement's keyword in must be an iterable. b. An iterable is an object from which the for statement can take one item at a time until no more items remain. c. One of Python's most common iterable sequences is the list, which is a comma-separated collection of items enclosed in square brackets ([ and ]). d. The following code totals five integers in a list: total = 0 for number in [2, -3, 0, 17, 9]: total + number

d. Actually, change the statement in the for's suite from total + number to total = total + number for the code to total the five elements in the list.

Which of the following statements is false? a. Python stops evaluating an and-expression as soon as it knows whether the entire condition is False. Python stops evaluating an or-expression as soon as it knows whether the entire condition is True. b. The following condition stops evaluating immediately if gender is not equal to 'Female' because the entire expression must be False. If gender is equal to 'Female', execution continues, because the entire expression will be True if the age is greater than or equal to 65: gender == 'Female' and age >= 65 c. The following condition stops evaluating immediately if semester_average is greater than or equal to 90 because the entire expression must be True: semester_average >= 90 or final_exam >= 90 d. In operator expressions that use the and operator, make the condition that's more likely to be True the leftmost condition—in or operator expressions, make the condition that's more likely to be False the leftmost condition—each of these tactics can reduce a program's execution time.

d. Actually, in operator expressions that use the and operator, make the condition that's more likely to be False the leftmost condition—in or operator expressions, make the condition that's more likely to be True the leftmost condition—each of these tactics can reduce a program's execution time.

Which of the following statements is false? a. In top-down, stepwise refinement, the top is a single statement that conveys the program's overall function but rarely conveys enough detail from which to write a program. b. The top specifies what should be done, but not how to implement it. c. In the refinement process, we decompose the top into a sequence of smaller tasks—a process sometimes called divide and conquer. d. In the top-down, stepwise refinement process for developing algorithms, each refinement represents another portion of the algorithm.

d. Actually, in the top-down, stepwise refinement process for developing algorithms, each refinement represents the complete algorithm—only the level of detail varies.

Which of the following statements is false? a. Each sequence has an iterator. b. The for statement uses the iterator "behind the scenes" to get each consecutive item until there are no more to process. c. The iterator is like a bookmark—it always knows where it is in the sequence, so it can return the next item when it's called upon to do so. d. Lists are unordered and a list's items are mutable.

d. Actually, lists are ordered (and mutable).

Which of the following statements is false? a. The following f-string inserts the value of average into a string: f'Class average is {average}' b. You specify where to insert values in an f-string by using placeholders delimited by curly braces ({ and }). c. The placeholder {average} converts the variable average's value to a string representation, then replaces {average} with that replacement text. d. Replacement-text expressions in placeholders may contain values, variables or other expressions, such as calculations, but may not contain function calls.

d. Actually, replacement-text expressions may contain values, variables or other expressions, such as calculations or function calls.

Which of the following statements is false? a. Many applications require precise representation of numbers with decimal points. b. Financial institutions like banks that deal with millions or even billions of transactions per day have to tie out their transactions "to the penny." Floating-point numbers can represent some but not all monetary amounts with to-the-penny precision. c. For monetary calculations and other applications that require precise representation and manipulation of numbers with decimal points, the Python Standard Library provides type Decimal, which uses a special coding scheme to solve the problem of "to-the-penny precision." Banks also have to deal with other issues such as using a fair rounding algorithm when they're calculating daily interest on accounts. Type Decimal offers such capabilities. d. Floating-point values are stored and represented precisely in binary format.

d. Actually, some floating-point values are represented only approximately when they're converted to binary.

Which of the following statements is false? a. Executing a break statement in a while or for immediately exits that statement. b. The following snippet produces the integer sequence 0 1 2 3 4 5 6 7 8 9: for number in range(100): if number == 10: break print(number, end=' ') c. The while and for statements each have an optional else clause that executes only if the loop terminates normally. d. The following code snippet produces the sequence 0 1 2 3 4 5 5 6 7 8 9: for number in range(10): if number == 5: continue print(number, end=' ')

d. Actually, the code snippet produces the sequence 0 1 2 3 4 6 7 8 9.

Which of the following statements is false? a. Python provides three types of selection statements that execute code based on a condition—any expression that evaluates to either True or False. b. The if...else statement performs an action if a condition is True or performs a different action if the condition is False. c. Anywhere a single action can be placed, a group of actions can be placed. d. The if...elif...else statement is called a double-selection statement because it selects one of two different actions (or groups of actions).

d. Actually, the if...elif...else statement is called a multiple-selection statement because it selects one of many different actions (or groups of actions).

Which of the following statements is false? a. Function range's one-argument version produces a sequence of consecutive integers from 0 up to, but not including, the argument's value. b. The following snippet produces the sequence 5 6 7 8 9. for number in range(5, 10): print(number, end=' ') c. The following snippet produces the sequence 0 2 4 6 8. for number in range(0, 10, 2): print(number, end=' ') d. The following snippet produces the sequence 10 8 6 4 2 0. for number in range(10, 0, -2): print(number, end=' ')

d. Actually, the snippet produces the sequence 10 8 6 4 2.