Python Basics

Question 1

Create function with default argument

Answer 1

def student(firstname, lastname =’Mark’):
pass

Question 2

Loop through elements in an array

Answer 2

for element in array:
pass

Question 3

Check if a variable is an array

Answer 3

type(array) is list

Question 4

Decode and parse a URL

Answer 4

from urllib.parse import urlparse, parseqs
URL=’https://someurl.com/with/query_string?i=main&enc=+Hello’
parsed_url = urlparse(URL)
parse_qs(parsed_url.query)

Question 5

Increment a variable number by 1

Answer 5

n += 1 (note, n++ is not valid Python syntax)

Question 6

Return minimum value in array

Answer 6

min(1, 2, 3)

Question 7

Loop through index and value of elements in an array

Answer 7

for idx, value in enumerate(arr):
pass

Question 8

Add element to end of list

Answer 8

myList.append(value)

Question 9

Round a float number to an integer

Answer 9

round(n)

Question 10

How can you write a number in python using a thousands place delimeter

Answer 10

num = 16_000

Question 11

How do you indicate that a number is binary?

Answer 11

Prefix with 0b, example 0b0101

Question 12

What number is this binary value, 10101

Answer 12

The 4 digits represent 16-8-4-2-1
Therefore this is calculated as 16 + 0 + 4 + 0 + 1 = 21

Question 13

How do you negate / reverse a result?

Answer 13

not True # use the ‘not’ keyword

Question 14

Write a full if statement with different conditions

Answer 14

if a > b:
pass
elif b > a:
pass
else:
pass

Question 15

Print numbers 1 through 100

Answer 15

for i in range(1, 101):
print(i)

Question 16

Print numbers from 100 to 1

Answer 16

for i in range(100, 0, -1):
print(i)

Question 17

How do you determine the size of a list?

Answer 17

len(myList)

Question 18

Add a new value to the end of a list

Answer 18

myList.append(‘new value’)

Question 19

Remove the last element of a list

Answer 19

myList.pop()

Question 20

Loop through values in a list

Answer 20

for value in [1, 2, 3, 4]:
print(value)

Question 21

Set variables to the max and min numbers possible

Answer 21

negative_infinity = float(‘-inf’)
positive_infinity = float(‘inf’)

Question 22

Return every other element from a list

Answer 22

myList[::2]

Question 23

Return the last 2 elements from a list

Answer 23

myList[-2:]

Question 24

Combine to lists

Answer 24

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

Question 25

Determine whether an item is in a list

Answer 25

“my item” in myList

Question 26

Delete the second element from a list

Answer 26

del myList[1]

Question 27

Delete the second and third elements from a list

Answer 27

del myList[1:3]

Question 28

Delete all elements from a list

Answer 28

del myList[:]

Question 29

How do you add an element to a tuple

Answer 29

You can’t. They’re a fixed size

Question 30

Create a tuple with one item

Answer 30

myTuple = (“myItem”,) // OR tuple(“myItem”)
// You must include a comma so Python knows it’s a tuple

Question 31

Given a sentence, create a list of the words

Answer 31

words = message.split()

Question 32

Given a list of words, create a sentence from them

Answer 32

” “.join(words)

Question 33

Given an array, divide it in half evenly between two separate arrays without using a loop

Answer 33

myArray[::2], myArray[1::2]

Question 34

Delete a key from a dictionary

Answer 34

del my_dict[“my_key”]
// an error is thrown if the key doesn’t exist

Question 35

Check if a key exists within a dictionary

Answer 35

“my_key” in my_dict

Question 36

Increment the value of a dictionary key

Answer 36

my_dict[my_key] += 1

Question 37

Iterate through keys in a dictionary

Answer 37

for key in my_dict:
pass

Question 38

Determine how many keys are present in a dictionary

Answer 38

len(my_dict)

Question 39

Are Python dictionaries ordered?

Answer 39

Yes, as of Python version 3.7 (they are unordered in Python 3.6 and earlier)

Question 40

Combine two Python dictionaries

Answer 40

first_dict | second_dict

Question 41

How do you create and use a set in Python (including iterating through one)?

Answer 41

fruits = {‘apple’, ‘banana’} // or, fruits = set() or fruits = set([‘apple’, ‘banana’])
fruits.add(‘grape’)
fruits.remove(‘apple’)
for fruit in fruits:
pass
// you can also pass a list to a set to convert it, eg set(myList)

Question 42

Find all the items that are present in one list but not another

Answer 42

list(set(first_list) - set(second_list))
// You can subtract the elements in one Set from another Set using the - operator

Question 43

What are two kinds of errors in Python?

Answer 43

Syntax errors: code that isn’t adhering to proper Python syntax
Exceptions: an execution error, eg 10 / 0; these can be handled using a try-except pattern

Question 44

Handle an exception error

Answer 44

try:
10 / 0
except Exception as e:
print(e)

Question 45

How do you throw an error

Answer 45

raise Exception(“here is the error”)
// or, raise ValueError(“”) etc

Question 46

How can you check if a variable is an integer, floating point number, or string?

Answer 46

type(n) == int
type(n) == float
type(n) == str

Question 47

Create a class called wall that has armor value initialized at 10 and a height value initialized at passed in value and a method to double the height

Answer 47

class Wall:
height = 10 // this is a class variable (don’t use them because all instances of this class will share this global value, which can be changed by any of the instances)

def __init__(self, armor):
// this is referred to as the constructor
self.armor = armor // this is an instance variable as it’s specific to an instance

def double_height(self):
Wall.height *= 2

my_wall = Wall(5) // this “object” is called an “instance” of the Wall class

Question 48

Convert a string to lowercase

Answer 48

“My String”.lower()

Question 49

Remove an item from a list based on value (not index)

Answer 49

my_list.remove(value)

Question 50

How do you make a property or method private within a class?

Answer 50

Prefix with two underscores, eg self.__armor

Question 51

What is encapsulation?

Answer 51

It’s for hiding internal state / implementation details (like private properties and methods)

Question 52

What is abstraction?

Answer 52

It’s about creating a simple interface for complex behavior that’s easy to use
Getting abstractions right is crucial because changing them later can be disastrous

Question 53

What is inheritance?

Answer 53

Allows one class (the “child’) to inherit the properties of another class (the “parent”)

Question 54

Create a cow class that inherits from the animal class

Answer 54

class Animal:
def __init__(self, num_legs):
self.num_legs = num_legs

class Cow(Animal):
def __init__(self):
super().__init__(4) # call the parent constructor

Question 55

Create an empty array of n elements

Answer 55

[None for _ in range(n)]

Question 56

Sort an array in descending order

Answer 56

my_array.sort(reverse=True)

Question 57

Get the absolute value of a number

Answer 57

abs(n)

Question 58

Return the value of a given dictionary key, otherwise return null if the key doesn’t exist

Answer 58

my_dict.get(key, None)

Question 59

Determine if list contains a value

Answer 59

any(value == ‘a’ for value in my_list)