CSIS 150 exam 2

What will the output of the following code be?

x = 7
if x > 10:
    print("Greater than 10")
elif x > 5:
    print("Greater than 5 but less than or equal to 10")
else:
    print("5 or less")

greater than 5 but less then or equal to 10 

What will the following code output?

x = 8
y = 12
if x < 10 and y > 10:
    print("Condition met")
else:
    print("Condition not met")

condition met 

will this evaluate to True or False: 5>3 and not (6<1)

True

What will the following code print?

x = 21
if x % 2 == 0:
    print("x is even")
else:
    if x % 3 == 0:
        print("x is magically odd")
    else:
        print("x is odd")

x is magically odd

(Challenging) What will the following code output?

a = 4
b = 15
if (a % 2 == 0 or b % 2 == 0) and not (a > 10 or b < 5):
    print("Condition 1")
elif a * b > 40 and (a % 3 == 0 or b % 3 == 0):
    print("Condition 2")
else:
    print("Condition 3")

Condition 1 

which list method will add a single element to the end of the list

append()

What will be the output of the following code?

my_string = "Hello"
new_string = ""
for i, char in enumerate(my_string):
    if i % 2 == 0:
        new_string += char.upper()
    else:
        new_string += char.lower()
print(new_string)

HeLlO

What will be the result of running this code?

numbers = [1, 2, 3, 4]
numbers.append([5, 6])
print(numbers)

[1, 2, 3, 4, [5, 6]]

Read this code  and determine the output of running this code?

my_list = [1, 2, 3]
new_list = my_list
new_list[2] = 6
print(my_list)

[1, 2, 6]

(Challenging) Read this code carefully and determine the output of running this code?

my_list = [1, 2, 3]
new_list = my_list
new_list = [4, 5, 6]
print(my_list)

[1, 2, 3]

what is the primary different between a for loop and a while loop

A for loop runs a fixed number of times, while a while loop runs indefinitely until a condition becomes false

which of the following conditions would case a while loop to execute indefinitely

while true with no break statement and while x > 0 where x is never modified 

when does the break statement exit a loop

immediately upon encountering the break statement

What happens when the continue statement is executed in a while loop?

The loop continues with the next iteration, skipping the rest of the current iteration.

What is the output when the following code executes?

x = 0
while x < 5:
    if x == 2:
        break
    x += 1
print(x)

2

what will the following code do?

x = 10
while x > 0:
    x -= 2
    if x % 3 == 0:
        continue
    print(x)

prints all values of x as it decrease by 2, skipping the values where x is divisible by 3

which Path method can be used to check if a Path object exists as a file or directory in the file system

exists()

Given the following code, what does it return?

from pathlib import Path
p = Path('data.txt')
print(p.is_dir())

False if data.txt is a file and true if data.txt is a directory

Given the following code, what will be printed?

from Pathlib import Path

testfile = Path('example.txt')
with open(testfile, 'w') as f:
    f.write('Hello, World!')
with open(testfile, 'r') as f:
    print(f.read())

‘Hello, World!’

which of the following is a correct way to open a file for reading in Python

file = open(‘example.txt’, ‘r’)

which file handle method lets you read all the lines from a file into a list 

readlines()

What does the with context manager do when working with files? (Select all correct answers)

it ensures the file is properly closed after its context block of code finishes and it opens the file 

what is the correct syntax for defining a function that takes parameters in python

def name(parameters)

what does the return statement do in a function

it stops the function and returns a value 

What will the following code output?

def greet():
    return "Hello, World!"


greet()

nothing (it outputs nothing) 

boolean

expressions either evaluate to True or False 

True in boolean

1

Flase in boolean

0

do strings evaluate to true or false in boolean

true

do empty strings and set evaluate to true or false in boolean

False

equality operator 

== - checks if the values are the same (true) or different (false)

inequality operator

! =, checks values not equal

assignment operator

=, makes x equal to a value

short circuit evaluation

or- only looks till a true, and- only looks till there is a false

in and not in operators

case sensitive and returns true or false

are == and ! = before or after not, and, or

before

what order do and, not, or evaluate in

not, and, or

nested conditionals

if statement inside an if statement

chained conditionals

elif statements

nested vs chained conditionals which is better 

based on readability 

mutable

can be changed after it is created, list

immutable

cannot be changed after it is created, strings, tuples

object

something a variable can refer to in memory

reference

when you assign the variable to an object and you create a reference to that object

Id() function 

shows the memory location of the variable 

is operator

returns true if they have the same memory location and returns false if they dont

aliasing

if two variables refer to the same thing, changing one can change both

cloning

making a copy of a list to not mess up the OG list

slice operator

the best way to copy a list [:]- takes the whole list

.copy()

copies to a new object, same id

.append()

adds the argument to the end of the list

.insert()

adds the second argument in the index indicated by the first argument .insert(1,2) adds 2 in the first spot 

.reverse()

reverses the order of the list in place

.sort()

sorts the list items in place (numerical or alphabetical)

.remove()

removes an item at the given index

.pop()

returns and removes the value of the last item in the list 

why is this bad code 

sorted_list = orginal_list.sort()

it destroys the list as the sort function returns nothing 

what is the difference between append and + when talking about lists

append combines elements and + adds the list together [1,2,3[4,5,6]] vs [1,2,3,4,5,6]

.sorted()

creates a copy of the sorted list

why are string methods not mutable

cause strings are not mutable

.split()

returns list of strings based on your parameters

.upper()

all uppercase

.lower()

all lowercase

.strip()

removes the white space (tabs, /n)

.replace()

replaces all occurrences of a substring with a new substring

example of .format()

greeting = 'hello my name is {} and i am a {}'. format(name,job)

print(greetings)

why should you not change the length of a list when iterating over it 

can lead to skipping values or an infinite loop 

definite iteration 

stops at a certain number 

indefinite iteration

keeps going ‘forever’ till it reaches a stop (false)

infinite loops

a while loop that will never become false

listener loop

repeat indefinitely till a particular input is given- make sure use input is valid

sentinel value

special value that signals the end of a loop