Python

Question 1

Find length of list

Answer 1

length = len(list)

Question 2

For loop for list

Answer 2

for element in list:

Question 3

If, elif, else

Answer 3

if condition1:

elif condition2:

else:

Question 4

If, elif, else

Answer 4

if condition1:

elif condition2:

else:

Question 5

Print value

Answer 5

print(value)

Question 6

Print floating point number with precision

Answer 6

print(f’{value:.6f}’)

Question 7

Initiate variable

Answer 7

variable = 0

Question 8

Increase a count

Answer 8

count += 1

Question 9

Decrease a count

Answer 9

count -= 1

Question 10

Initialise a variable to positive infinity

Answer 10

variable = float(‘inf’)

Question 11

Initialise a variable to negative infinity

Answer 11

variable = -float(‘inf’)

Question 12

Print multiple values in one line in Python

Answer 12

print(f’{value1} {value2}’)

Question 13

Replace a substring in a string in python

Answer 13

new_string = old_string.replace(‘old_substring’, ‘new_substring’)

Question 14

Check if substring in string

Answer 14

if ‘substring’ in string:

Question 15

How to get a substring of first n numbers of characters

Answer 15

substring = string[:2]

Question 16

Get substring of characters after first 2

Answer 16

substring = string[2:]

Question 17

Convert string to int

Answer 17

number = int(string)

Question 18

Convert number to string

Answer 18

str(number)

Question 19

Replace first occurrence of a substring in Python

Answer 19

new_string = old_string.replace(‘old_substring’, ‘new_substring’, 1)

Question 20

How to iterate from 1 to n inclusive in a for loop using range

Answer 20

for i in range(1, n+1)

Question 21

Iterate from 0 to n exclusive in a for loop using range

Answer 21

for i in range(n):

Question 22

Iterate from starting value to an ending value with a specific step in a for loop

Answer 22

for i in range(start, stop, end):

Question 23

How to check if a number is divisible by another number

Answer 23

number % division == 0

Question 24

Iterate backwards from n to 1 inclusive using range

Answer 24

for i in range(n, 0, -1):

Question 25

Sort list in place

Answer 25

list.sort()

Question 26

Find floor of a number

Answer 26

import math

math.floor(number)

Question 27

Find ceiling of a number

Answer 27

import math

math.ceil(number)

Question 28

Create an empty dictionary

Answer 28

dictionary = {}

Question 29

Check if key exists in dictionary

Answer 29

if key in dictionary:

Question 30

Delete key value pair

Answer 30

del dictionary[key]

Question 31

Add key value pair

Answer 31

dictionary[key] = value

Question 32

Get list of all keys in a dictionary

Answer 32

keys = list(dictionary.keys())

Question 33

Calculate the trace of diagonal elements

Answer 33

import numpy as np

np.trace(matrix)

Question 34

Transpose a matrix and find trace

Answer 34

import numpy as np

np.trace(matrix.T)

Question 35

Iterate through the rows of a square matrix

Answer 35

for i in range(len(matrix)):

Question 36

Access elements on the primary diagonal of a square matrix

Answer 36

matrix[i][i]

Question 37

Access element on the secondary diagonal of a square matrix

Answer 37

matrix[len(matrix) - 1 - i][i]

Question 38

Find absolute value of a number

Answer 38

abs(number)

Question 39

Initialise an array with zeros in Python

Answer 39

array = [0] * size

Question 40

Initialise an array with a specific value using list comprehension in Python

Answer 40

array = [value for x in range(size)]

Question 41

Initialise a list with a given size and fill with None values

Answer 41

array = [None] * size

Question 42

What is counting sort

Answer 42

Counting sort is a non-comprehension-based sorting algorithm that sorts integers by counting the number of occurrences of each unique element. It then calculates the positions of each element in the sorted array

Question 43

When to use Counting Sort

Answer 43

Counting sort is efficient when the range of input values (k) is not significantly larger than the number of elements (n) to be sorted. It is ideal for sorting integers within a limited range

Question 44

Time complexity of counting sort

Answer 44

O(n+k) where n is the number of elements in the input array and k is the range of the input

Question 45

How to find the minimum value in a list in Python

Answer 45

min_value = min(list)

Question 46

Find maximum value in a list in Python

Answer 46

max_value = max(list)

Question 47

Calculate the range of elements in a list

Answer 47

range_of_elements = max_value - min_value

Question 48

Find maximum value of many values

Answer 48

max_value = max(value1, value2, value3, value4)

Question 49

Swap two elements in a list

Answer 49

list[index1], list[index2] = list[index2], list[index1]

Question 50

Unpack a list into separate arguments

Answer 50

function(list)
print(list)

Question 51

Find index of a character in a string in Python

Answer 51

index = string.find(character)

Question 52

Get character at index Python

Answer 52

character = string[index]

Question 53

Concatenate string Python

Answer 53

result = string1 + string2

Question 54

Check if character in string

Answer 54

if character in string

Question 55

Create a list with list comprehension

Answer 55

new_list = [expression for item in iterable]

Question 56

Iterate from both ends of a string towards the center

Answer 56

left, right = 0, len(string) - 1
while left < right:
#proces
left += 1
right -= 1

Question 57

Check if string is a palindrome

Answer 57

string == string[::-1]

Question 58

Slice a string to remove character at index

Answer 58

new_string = string[:index] + string[index+1:]

Question 59

Sort each row in a 2D list in Python

Answer 59

sorted_grid = [sorted(row) for row in grid]

Question 60

How to sort in place

Answer 60

string.sort()

Question 61

Sort and return new string

Answer 61

sorted(string)

Question 62

Check if stack (list) is empty before accessing the top element

Answer 62

if stack and stack[-1] == element:

Question 63

Remove last element in stack

Answer 63

stack.pop()

Question 64

Remove element with index

Answer 64

stack.pop(index)

Question 65

Add to end of a list

Answer 65

list.append(value)

Question 66

Count occurrences of elements in a list using a dictionary in Python

Answer 66

string_counts = {}
for s in list_of_strings:
if s in string_counts:
string_counts[s] += 1
else:
string_counts[s] = 1

Question 67

Retrieve a value from a dictionary with a default if the key is not present. So we can have a value if there is no key

Answer 67

Example:

value = dictionary.get(key, default_value)

count = string_counts.get(query, 0)

Question 68

Make string lower case

Answer 68

str.lower()

Question 69

Make python string upper case

Answer 69

str.upper

Question 70

Convert string to a set. This is a set of unique characters

Answer 70

set(string)

Question 71

Check if a set is a subset of another set

Answer 71

set1.issubset(set2)

Where set1 is the constraint set like alphabet, so you would see if set2 contains the whole alphabet

Question 72

Convert first letter to capital in string

Answer 72

str.capitalise()

Question 73

Center a string after padding with a specified character

Answer 73

str.center(width, [fillchar])

E.g., str.center(24, ‘*’)

Question 74

Return number of occurrences of a substring in a given string

Answer 74

str.count(substring, start, end)

str.count(‘p’)

Question 75

Return true if a string ends with a specified suffix

Answer 75

str.endswith(‘PM’)

Question 76

Return index of first occurrence of substring if found, if not found returns -1

Answer 76

str.find(‘fun’)

Question 77

Return index of first occurrence of substring if found, if not found returns -1

Answer 77

str.find(‘fun’)

Question 78

Return true if all characters in string are alphanumeric, if not false

Answer 78

str.isalnum()

Question 79

Find if string is all alphabet characters, either upper or lower case

Answer 79

str.isalpha()

Question 80

Return true if all characters in a string are digits

Answer 80

str.isdigit()

Question 81

Return true if all characters are lower case

Answer 81

str.islower()

Question 82

Return true is all characters are upper case

Answer 82

str.isupper()

Question 83

Join all elements of an iterable list separated by a given separator

Answer 83

‘ ‘.join(array)

Question 84

Convert characters in a string to the opposite case

Answer 84

str.swapcase()

Question 85

Replace a substring with another string, this is for every occurrence

Answer 85

str.replace(‘ba’, ‘ro’)

Question 86

Split a string to an array with a chose separator

Answer 86

str.split()

str.split(separator)

Question 87

Split a string to an array with a chose separator

Answer 87

str.split()

str.split(separator)

Question 88

Sort list in ascending order

Answer 88

list.sort()

Question 89

Sort list in descending order

Answer 89

list.sort(reverse=True)

Question 90

Calculate the sum of a subarray

Answer 90

subarray_sum = sum(list[start:end])

Question 91

Calculate the sum of a subarray

Answer 91

subarray_sum = sum(list[start:end])

Question 92

Iterate over all possible subarrays of a given length

Answer 92

access the subarray with list[i:i+subarray_length]

for i in range(len(list) - subarray_length + 1):

Question 93

Remove value from array

Answer 93

stack.remove(num)

Question 94

Count occurrences of elements in a list using a dictionary

Answer 94

sock_counts = {}
for sock in list_of_socks:
if sock in sock_counts:
sock_counts[sock] += 1
else:
sock_counts[sock] = 1

Question 95

Iterate through values in dictionary

Answer 95

for value in dictionary.value():

Question 96

Calculate the number of pairs from a count of items

Answer 96

pairs = count // 2

This is integer division, essentially calculating the number of times 2 goes completely into pairs