ICS 31 Study Guide Questions and Answers

ICS 31 Study Guide Questions and AnswersWhat is one similarity between print() and input()? * Both generate a string output * Both are built-in or standard library functions When ever the Python interpreter needs to evaluate a name (of a variable, function, ...), it searched for the name in order: 1) 2) 3) 4) 1) local 2) Global 3)Module Import 4 ) Built in Explain the difference between 'import math' and 'from math import sqrt' or 'from math import*' 'Import math' and 'From math import' import all the functions/objects of the module while 'from module import sqrt' imports the specific function/object. "From math import' and 'From math import sqrt' allow the object to be referred to without including the module from which it was imported, which might lead to pollution of the name space. What is the difference between print() and return? * print(): prints the specified message to the screen * return : is used to end the execution of the function call and "returns" the result (value of the expression following the return keyword) to the caller * print example *return example Which operator has the lowest precedence? Why? count %= count - offset + 2 answer: (%=) explanation: Since the modulo operator is chained with the assignment operator(which has the lowest precedence), the %= will execute last. Do the keys in a dictionary best model a list or a set? + 5 pts [List or Set] Set + 5 pts [Uniqueness] Keys must be unique + 5 pts [Order] Keys and sets are unordered. + 5 pts [Mutability] Keys are immutable, and elements of a set have to be immutable Give two examples of functionality/applications that you can do with a dictionary you can't do with a list. + 2.5 pts Relationships between keys and values + 2.5 pts Addressing values by key rather than index Given a value for a dictionary, is there a built-in way to lookup the corresponding key? Explain your answer. + 4 pts There is NOT a built-in way. + 4 pts Keys are unique while values are not. + 4 pts Many keys might have the same associated value. Why does python provide so many different ways to structure & store data? What would happen if Python didn't provide data structure? +4 pts Answered first question: many ways to associate/store data +4 pts Programs would have an unmanageable number of variables Give two examples of functionality/applications that you can do with a dictionary you can't do with a list. + 2.5 pts Relationships between keys and values + 2.5 pts Addressing values by key rather than index + 2.5 pts Keys are unique + 2.5 pts Dictionaries are unordered When can you change the field of a namedtuple and not change the original object's id? Write a program to demonstrate. + 4 pts Answer: when the field being changed is a mutable object + 4 pts Example: nt = namedtuple('nt','immutable mutable') e = nt('s',[0]) d(1) Why is it good advise to use parentheses with Boolean expressions? *overrides operator precedence * for readability *you can use an example with the "and" and "or" operators to increase the precedence of the or operator What is the difference between a function that returns None and a value returning method? *a value returning method has a return statement, a function that returns None doesn't exist *result of a value returning method can be used in expressions(more commonly) Arguement the value that is sent to the function when its called Parameter a variable listed inside the parenthesis in a function's definition Why is it good advice to use parentheses with Boolean expressions? Give an example where it is necessary. + 4 pts override operator precedence + 4 pts For readability of a very long and unreadable boolean expression + 4 pts Example with both "and" and "or" operators where parentheses are used to increase the precedence of the "or" operato Why are the relational operators called "relational"? + 8 pts Compare two values to determine how they relate to one another (, , =, =, ==, !=) + 8 pts Makes a binary statement ranking two values Explain the differences between positive and negative indexing in Python. + 2.5 pts Start Index: positive uses '0', negative is -1 + 2.5 pts Incrementing: positive use +1, negative uses -1 + 2.5 pts Last Index: positive = len(lst)-1, negative = -len(lst) What is the main difference between looping-by-value and looping-by-index(as discussed during lecture)? Using code, give an example to describe your answer. Difference: Loop-By-Value 4 pts 2.1 Difference + 2 pts DIFFERENCE: Looping-by-Index allows direct access to containers original contents to be modified. 2.2 Example + 1 pts EXAMPLE: show loop-by-index: Header: for .... range(len())/enumerate __or__ while index len() + 1 pts EXAMPLE: show loop-by-index: Body/Change: lst[index] += 1 __or__ lst[index] += 1; index += 1 - 0.5 pts Your loop by value is a loop by index. + 0 pts Incorrect What is the problem with the program below? How would you fix it? numbers = list(range(lO)) for i in range(len(numbers)): if numbers[i] %2 == 0: del numbers[i] + 4 pts Problem Detection: deleting from a list while iterating over it + 2 pts Partially correct problem detection + 2 pts Solution: make a copy of the list + 2 pts Solution: use remove instead of delete with an index from list copy The Python code below is supposed to double the value of each element in a list. What are the problems with the program below? How would you fix it? data = [ 4 . 14, 7 . 2 3, 8 . 2 2] for i in range(data): i *= 2 + 8 pts Correct + 4 pts Problem Detection: deleting from a list while iterating over it + 4 pts Partially correct problem detection + 2 pts Solution: make a copy of the list + 2 pts Solution: use remove instead of delete with an index from list copy Write a function named, duplicate_ date, that takes three integers as parameters, representing a 2-digit month, 2-digit day, and 4-digit year. The function returns True when the combined value of the month-day, or daymonth are the same as the year, and False otherwise. Example: duplicate_date (10 ,25, 1025) returns True duplicate_date (25, 10, 1025) returns True duplicate_date (11, 22, 3333) returns False Write your program in a file named, duplicate_ & upload. Coding: duplicate_date + 0 pts Completely wrong + 1 pts return statement + 1 pts return true or false + 3 pts correct calculations + 2 pts one if/else or 'or' (for 'daymonth' or 'monthday') + 3 pts if/else or 'or' for both 'daymonth' and 'monthday' Write a function, get_longest_run(num_list), that returns the starting index in the array of a run of maximum size. A run is defined as the repeated occurrence of the same value in two or more consecutive positions in the array. If there are no runs return -1. get_longest_run([1, 2, 2]) - 1 get_longest_run([1, 2, 2, 99, 99, 99, 7]) - 3 get_longest_run([1, 11, 6, 7, 2]) - -1 getLongestRun + 10 pts Correct + 1 pts Loop through all elements + 2 pts Keep track of maximum run index + 2 pts Detect start/end of run + 2 pts Initialize run counter & incrementing + 2 pts Keep track of current run value + 1 pts Correct return value(-1 for no run) What is the difference between an argument & a parameter? Argument vs Parameter + 8 pts A parameter is initialized through an argument's value(passed through/into), an argument is the value passed through/into the function + 8 pts Not Expected: Correct answers pertaining to Scope/Mutability/ an argument lives outside the function's scope + 4 pts Partially Correct based on above statements + 3 pts Defined terms: parameter & argument, but did not explain a difference. + 2 pts Correctly defined one + 1 pts Not blank, but incorrect statements Compare & contrast how function parameters & local variables are similar/different. + 2 pts (SIMILARITY) Local in Scope + 2 pts (SIMILARITY) Scope extends from def to end of function + 2 pts (DIFFERENCE) Initialized in args vs explicitly What is the difference between a function that returns None and a value-returning function? None vs Value + 8 pts A value returning method has a return statement, a function that returns None does not + 8 pts Result of a value returning method can be used in expressions (more commonly) + 4 pts Partially Correct based on above statements + 1 pts Not blank, but incorrect statements