python MCQ 16-30

Question 16. Please complete the script so that it prints out the value of key b .

print(d["b"])

Question 17. Calculate the sum of the values of keys a and b .

print(d["b"] + d["a"])

It's as easy as that. However, if you want to do the sum of all dictionary values you need to take another approach instead of accessing all values one by one. We're going through that approach later on in another exercise.

Question 18. What’ll be happened to execute, if face error try to solve.

There is no key Smith in the dictionary. Smith is a value. You want to use Surname if you want to access Smith :

print(d["Surname"])

A KeyError always means Python could not find a key with the name shown next to KeyError (e.g. Smith ).

Question 19. Add a new pair of key (e.g. c ) and value (e.g. 3 ) to the dictionary and print out the new dictionary.

d = {"a": 1, "b": 2} d["c"] = 3 print(d) Explanation: Adding pairs of keys and values is straightforward as you can see. Note though that you cannot fix the order of the dictionary items. Dictionaries are unordered collections of items.

Question 20. Calculate the sum of all dictionary values.

d = {"a": 1, "b": 2, "c": 3} print(sum(d.values())) Explanation: d.values() returns a list-like dict_values object while the sum function calculates the sum of the dict_values items.

Question 21. Question: Filter the dictionary by removing all items with a value of greater than 1.

d = {"a": 1, "b": 2, "c": 3} d = dict((key, value) for key, value in d.items() if value <= 1) print(d) Explanation: Here we're using a dictionary comprehension. The comprehension is the expression inside dict() . The comprehension iterates through the existing dictionary items and if an item is less or equal to 1,the item is added to a new dict. This new dict is assigned to the existing variable d so we end up with a filtered dictionary in d.

Question 22. Create a dictionary of keys a, b, c where each key has as value a list from 1 to 10, 11 to 20, and 21 to 30 respectively. Then print out the dictionary in a nice format.

from pprint import pprint d = dict(a = list(range(1, 11)), b = list(range(11, 21)), c = list(range(21, 31))) print(d) Explanation: We're using ranges here to construct the lists. We're also using the built-in Python pprint module which is used to print out well formatted views of datatypes in Python.

Question 23. Access the third value of key b from the dictionary.

from pprint import pprint d = dict(a = list(range(1, 11)), b = list(range(11, 21)), c = list(range(21, 31))) print(d['b'][2])

Question 24. Please complete the script so that it prints out the expected output.

d = dict(a = list(range(1, 11)), b = list(range(11, 21)), c = list(range(21, 31))) for key, value in d.items(): print(key, "has value", value)

Question 25. Make a script that prints out letters of English alphabet from a to z, one letter per line in the terminal.

import string for letter in string.ascii_lowercase: print(letter) Explanation: string is a built-in module and string.ascii_lowercase returns a string object containing all 26 letters of English alphabet. Then we simply iterate through that string and print out the string items.

Question 26. Make a script that prints out numbers from 1 to 10

for i in range(1,11): print(i) Explanation: A for loop is used to repeat an action (i.e. print ) until the iterating sequence (i.e. range ) is consumed. In our case it would print all items of the range one by one.

Question 27. Create a function that calculates acceleration given initial velocity v1, final velocity v2, start time t1, and end time t2.

Answer (Python 3):

def acceleration(v1, v2, t1, t2):
                                a = (v2 - v1) / (t2 - t1)
                                return a
        
                            print(acceleration(0,10,0,20))
                            Explanation (Python 3): 
        
                            The first three lines are where we create the function. A function definition is like a like a blueprint. Then in the last line we're printing out the function output. The output is whatever is returned by the return  statement.
        
                            Answer (Python 2): 
        
                            def acceleration(v1, v2, t1, t2):
                                a = float(v2 - v1) / float(t2 - t1)
                                return a
        
                            print(acceleration(0,10,0,20))
                            Explanation (Python 2): 
        
                            If you were creating this in Python 2 the solution would need to have two float  functions converting the two differences to float numbers because if the differences are integers, Python will also output an integer (e.g. 3 / 2 outputs 0). In Python 3 you don't have to convert to floats.

Question 28. Why is there an error in the code and how would you fix it?

Line 4 throws a TypeError because Python cannot multiply a None type object with an integer. The function output is what produces a None object because the function definition is not returning anything. Fix it by using return instead of print :

Question 29. Please write a function that calculates liquid volume in a sphere using the following formula. The radius r is always 10, so consider making it a default parameter.

Question 30. Why do you get an error and how would you fix it?

python MCQ 16-30

Answer 16.

Answer 17.

Answer 18.

print(d["Surname"])

Answer 19.

Answer 20.

Answer 21.

Answer 22.

Answer 23.

Answer 24.

Answer 25.

Answer 26.

Answer 27.

Answer 28.

Answer 29.

Answer 30.