Python - List Questions

Question 1

a = [1,2,3,4,5,6,7,8]

a[1:4]

Answer 1

a = [1,2,3,4,5,6,7,8]
a[1:4]

returns [2,3,4]

indexes at 0 and does NOT include the last index

Question 2

a = [1,2,3,4,5,6,7,8]

a[1:4:2]

Answer 2

a = [1,2,3,4,5,6,7,8]

a[1:4:2]

returns [2, 4]

slices along increments of 2 starting at your first index listed

Question 3

a = [1,2,3,4,5,6,7,8]

a[ : : -1]

Answer 3

a = [1,2,3,4,5,6,7,8]

a[ : : -1]

returns [8, 7, 6, 5, 4, 3, 2, 1]

slices the list in reverse

Question 4

a = [1, 2, 3, 4, 5]

sliceObj = slice(1, 3)

a[sliceObj]

Answer 4

a = [1, 2, 3, 4, 5]

sliceObj = slice(1, 3)

a[sliceObj]

return [2, 3]

Question 5

lst = [x ** 2 for x in range (1, 11) if x % 2 == 1]

Answer 5

lst = [x ** 2 for x in range (1, 11) if x % 2 == 1]

x ** 2 is output expression,
range (1, 11) is input sequence,
x is variable and
if x % 2 == 1 is predicate part.

Question 6

odd_square = [x ** 2 for x in range(1, 11) if x % 2 == 1]

print odd_square

Answer 6

odd_square = [x ** 2 for x in range(1, 11) if x % 2 == 1]
print odd_square

list contains square of all odd numbers from range 1 to 10

Question 7

power_of_2 = [2 ** x for x in range(1, 9)]

print power_of_2

Answer 7

power_of_2 = [2 ** x for x in range(1, 9)]

print power_of_2

list contains power of 2 from 1 to 8

Question 8

noprimes = [j for i in range(2, 8) for j in range(i*2, 50, i)]

primes = [x for x in range(2, 50) if x not in noprimes]

print primes

Answer 8

list contains prime and non-prime in range 1 to 50

noprimes = [j for i in range(2, 8) for j in range(i*2, 50, i)]

primes = [x for x in range(2, 50) if x not in noprimes]

print primes

Question 9

print [x.lower() for x in [“A”, “B”, “C”]]

Answer 9

print [x.lower() for x in [“A”, “B”, “C”]]

list for lowering the characters

Question 10

string = “my phone number is : 11122 !!”

print(“\nExtracted digits”)
numbers = [x for x in string if x.isdigit()]
print numbers

Answer 10

string = “my phone number is : 11122 !!”

print(“\nExtracted digits”)
numbers = [x for x in string if x.isdigit()]
print numbers

list which extracts number

Question 11

a = 5
table = [[a, b, a * b] for b in range(1, 11)]

print(“\nMultiplication Table”)
for i in table:
print i

Answer 11

a = 5
table = [[a, b, a * b] for b in range(1, 11)]

print(“\nMultiplication Table”)
for i in table:
print i

A list of list for multiplication table

Question 12

lst = filter(lambda x : x % 2 == 1, range(1, 20))

print lst

Answer 12

#  filtering odd numbers
lst = filter(lambda x : x % 2 == 1, range(1, 20))
print lst

Question 13

We can use FILTER function to filter a list based on some condition provided as a ___________ as first argument and list as second argument.

Answer 13

We can use FILTER function to filter a list based on some condition provided as a ___________ as first argument and list as second argument.

lambda expression

Question 14

lst = filter(lambda x : x % 5 == 0,
[x ** 2 for x in range(1, 11) if x % 2 == 1])
print lst

Answer 14

#  filtering odd square which are divisble by 5
lst = filter(lambda x : x % 5 == 0, 
      [x ** 2 for x in range(1, 11) if x % 2 == 1])
print lst

Question 15

lst = filter((lambda x: x < 0), range(-5,5))

print lst

Answer 15

#   filtering negative numbers
lst = filter((lambda x: x < 0), range(-5,5))
print lst

Question 16

print reduce(lambda a,b: a if (a > b) else b, [7, 12, 45, 100, 15])

Answer 16

#  implementing max() function, using
print reduce(lambda a,b: a if (a > b) else b, [7, 12, 45, 100, 15])

Question 17

“in” operator

Answer 17

“in” operator: This operator is used to check if an element is present in the list or not. Returns true if element is present in list else returns false.

ex) lis = [1, 4, 3, 2, 5]
if 4 in lis:
print ….

Question 18

“not in” operator

Answer 18

“not in” operator : This operator is used to check if an element is not present in the list or not. Returns true if element is not present in list else returns false.

ex) lis = [1, 4, 3, 2, 5]
if 4 not in lis:
print ….

Question 19

len()

Answer 19

len() : This function returns the length of list.

Question 20

min()

Answer 20

min() :- This function returns the minimum element of list.

Question 21

max()

Answer 21

max() :- This function returns the maximum element of list.

Question 22

+ operator

Answer 22

“+” operator :- This operator is used to concatenate two lists into a single list.

Question 23

• operator

Answer 23

“*” operator :- This operator is used to multiply the list “n” times and return the single list.

Question 24

index(ele, beg, end)

Answer 24

index(ele, beg, end) :- This function returns the index of first occurrence of element after beg and before end.

# using index() to print first occurrence of 3
# prints 5
print ("The first occurrence of 3 after 3rd position is : ", end="")
print (lis.index(3, 3, 6))

Question 25

count()

Answer 25

count() :- This function counts the number of occurrences of elements in list.

# using count() to count number of occurrence of 3
print ("The number of occurrences of 3 is : ", end="")
print (lis.count(3))

Question 26

del[a : b]

Answer 26

del[a : b] :- This method deletes all the elements in range starting from index ‘a’ till ‘b’ mentioned in arguments.

Question 27

pop()

Answer 27

pop(): This method deletes the element at the position mentioned in its arguments.

Question 28

insert(a, x)

Answer 28

insert(a, x) :- This function inserts an element at the position mentioned in its arguments. It takes 2 arguments, position and element to be added at respective position.

Question 29

remove()

Answer 29

remove() :- This function is used to delete the first occurrence of number mentioned in its arguments.

Question 30

sort()

Answer 30

sort() :- This function sorts the list in increasing order.

Question 31

reverse()

Answer 31

reverse() :- This function reverses the elements of list.

Question 32

extend(b)

Answer 32

extend(b) :- This function is used to extend the list with the elements present in another list. This function takes another list as its argument.

Question 33

clear()

Answer 33

clear() :- This function is used to erase all the elements of list. After this operation, list becomes empty.