Data Structures Assessment Test

Question 1

Describe the types of numbers used in python.

Answer 1

Floating points (float) ∈ R,

Integers (int) ∈ Z.

Question 2

Describe what are strings.

Answer 2

Ordered sequence of characters.

Question 3

Describe what are lists.

Answer 3

Ordered sequence of objects (mutable).

Question 4

Describe what are tuples.

Answer 4

Ordered sequence of objects (immutable).

Question 5

Describe what are dictionaries.

Answer 5

Key-value pairing that is unordered.

Question 6

What would you use to find a number’s square root?

Answer 6

x**0.5

Question 7

Reverse the string ‘hello’ using slicing.

Answer 7

s[: :-1].

Question 8

Build this list [0,0,0] two serarate ways.

Answer 8

Method 1: [0]*3

Method 2: list2 = [0,0,0], list2.

Question 9

Sort the list below:

list4 = [5,3,4,6,1].

Answer 9

sorted(list4)

or

list4.sort()

list4.

Question 10

Grab hello from the dictionary,

d = {‘k1’ : [{‘nest_key’ : [‘this is deep’, [‘hello’] ] } ] }.

Answer 10

d[‘k1’][0][‘nest_key’][1][0].

Question 11

Grab ‘hello’ from the dictionary below:

d = {‘k1’:[1,2,{‘k2’:[‘this is tricky’,{‘tough’:[1,2,[‘hello’]]}]}]}.

Answer 11

d[‘k1’][2][‘k2’][1][‘tough’][2][0].

Question 12

Can you sort a dictionary? Why or why not?

Answer 12

No, because normal dictionaries are mappings not a sequence.

Question 13

What is the major difference between tuples and lists?

Answer 13

List are mutable, tuples are immutable.

Question 14

How do you create a tuple t with items of 1,2,3?

Answer 14

t = (1,2,3).

Question 15

What is unique about a set?

Answer 15

They don’t allow for duplicate items.

Question 16

Use a set ot find unique values of the list below:

list5 = [1,2,2,33,4,4,,11,22,3,3,2].

Answer 16

set(list5).

Question 17

In python, is this statement true/false?

3.0 == 3.

Answer 17

True.

No approximations needed in python.

Question 18

In python, is this statement true/false?

4**0.5 != 2.

Answer 18

False.

0.5 is a binary fraction. No approximation is needed which means no floating point errors are made in python so 4**0.5 ==2.

Question 19

Why doesn’t 0.2 + 0.1 - 0.3 == 0.0 in python?

Answer 19

Python uses binary fractions to estimate all fractions. So every fraction that cannot be accurately represented by a binary fraction (1/2^x) will be approximated and will carry approximation errors.

In python,

0.2 + 0.1 - 0.3 == 5.551115123125783e-17.