Midterm material
How many else blocks can an if have?
One
What is the output?
nums = [10, 20, 30, 40]
print(nums[2])
30
What is the difference between an accessor method and a mutator method?
An accessor reads/returns an object’s data without changing it. A mutator changes the object’s data.
What is the main requirement for binary search?
The data must already be sorted
What is the difference between "w" mode and "a" mode when opening a file?
"w" writes new contents and erases existing contents, while "a" adds new data to the end of the file without removing existing contents.
What is the output?
def calculate(x, y): # start function
x = x + 2 # inside function
y = y * x # inside function
return y - x # inside function
# end function
a = 3
b = 4
print(calculate(a, b))
15
What does this print?
def mystery(n):
if n == 0:
print("Go")
else:
print(n)
mystery(n - 1)
#This is out of the function
mystery(3)
3
2
1
Go
what is the output?
class Car: # start class
def __init__(self, speed): # start constructor
self.__speed = speed
# end constructor
def accelerate(self, n): # start method
self.__speed += n
# end method
def get_speed(self): # start method
return self.__speed
# end method
# end class
a = Car(10)
b = a
b.accelerate(20)
print(a.get_speed())
30
What is the main difference between linear search and binary search?
Linear search checks values one by one.
Binary search repeatedly eliminates half of the remaining values.
What is an exception, and what happens if an exception is not handled?
An exception is a problem that occurs while a program is running. If it is not handled, the program stops and prints a traceback.
total = 0
for i in range(1, 5): # start for loop
for j in range(i): # start inner for loop
total += j # inside inner for loop
# end inner for loop
total += i # inside outer for loop
# end outer for loop
print(total)
20
What is the output?
def mystery(n):
if n == 0:
return 1
return n + mystery(n - 1)
#out of the function
print(mystery(4) * 2)
22
Explain the difference between an instance variable and a class variable.
An instance variable belongs to one object; each object has its own value.
A class variable is shared by all objects of the class.
Explain the main difference between selection sort and merge sort.
Selection sort repeatedly finds the smallest remaining value and puts it in its correct position.
Merge sort repeatedly divides the list into halves, sorts them, and then merges them back together.
What is the final content of scores.txt?
Assume it initially contains 80.
with open("scores.txt", "a") as file:
file.write("\n90")
# end with
with open("scores.txt", "w") as file:
file.write("100\n")
file.write("70")
# end with
with open("scores.txt", "a") as file:
file.write("\n60")
# end with
100
70
60