Loops Interview questions:
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1. x = [“ab”, “cd”]
for i in x:
i.upper()
print(x)
a) [‘ab’, ‘cd’]
b) [‘AB’, ‘CD’]
c) [None, None]
d) none of the mentioned
Answer: a
Explanation: The function upper() does not modify a string in place, it returns a new string that isn’t being stored anywhere
2. x = ["ab", "cd"]
for i in x:
x.append(i.upper())
print(x)
a) [‘AB’, ‘CD’]
b) [‘ab’, ‘cd’, ‘AB’, ‘CD’]
c) [‘ab’, ‘cd’]
d) none of the mentioned
Answer: d
Explanation: The loop does not terminate as new elements are being added to the list in each iteration.
3. i = 1
while True:
if i%3 == 0:
break
print(i)
i + = 1 =è space is the error (+=)
a) 1 2
b) 1 2 3
c) error
d) none of the mentioned
Answer: c
Explanation: SyntaxError, there shouldn’t be a space between + and = in +=.
4. i = 1
while True:
if i%0O7 == 0:
break
print(i)
i += 1
a) 1 2 3 4 5 6
b) 1 2 3 4 5 6 7
c) error
d) none of the mentioned
Answer: a
Explanation: Control exits the loop when i becomes 7.
5. i = 5
while True:
if i%0O11 == 0: # print(int(0O11)) ==> 9
break
print(i)
i += 1
a) 5 6 7 8 9 10
b) 5 6 7 8
c) 5 6
d) error
Answer: b
Explanation: 0O11 is an octal number.
6. i = 5
while True:
if i%0O9 == 0:
break
print(i)
i += 1
a) 5 6 7 8
b) 5 6 7 8 9
c) 5 6 7 8 9 10 11 12 13 14 15 ….
d) error
Answer: d
Explanation: 9 isn’t allowed in an octal number
7. i = 1
while True:
if i%2 == 0:
break
print(i)
i += 2
a) 1
b) 1 2
c) 1 2 3 4 5 6 ………………
d) 1 3 5 7 9 11 ……………..
Answer: d
Explanation: The loop does not terminate since i is never an even number.
8. i = 2
while True:
if i%3 == 0:
break
print(i)
i += 2
a) 2 4 6 8 10 …
b) 2 4
c) 2 3
d) error
Answer: b
Explanation: The numbers 2 and 4 are printed. The next value of i is 6 which is divisible by 3 and hence control exits the loop.
9. i = 1
while False:
if i%2 == 0:
break
print(i)
i += 2
a) 1
b) 1 3 5 7 …
c) 1 2 3 4 …
d) none of the mentioned
Answer: d
Explanation: Control does not enter the loop because of False.
10. True = False
while True:
print(True)
break
a) True
b) False
c) None
d) none of the mentioned
Answer: d
Explanation: SyntaxError, True is a keyword and it’s value cannot be changed.
11. i = 0
while i < 5:
print(i)
i += 1
if i == 3:
break
else:
print(0)
a) 0 1 2 0
b) 0 1 2
c) error
d) none of the mentioned
Answer: b
Explanation: The else part is not executed if control breaks out of the loop.
12. i = 0
while i < 3:
print(i)
i += 1
else:
print(0)
a) 0 1 2 3 0
b) 0 1 2 0
c) 0 1 2
d) error
Answer: b
Explanation: The else part is executed when the condition in the while statement is false.
13. x = "abcdef"
while i in x:
print(i, end=" ")
a) a b c d e f
b) abcdef
c) i i i i i i …
d) error
Answer: d
Explanation: NameError, i is not defined.
14. x = "abcdef"
i = "i"
while i in x:
print(i, end=" ")
a) no output
b) i i i i i i …
c) a b c d e f
d) abcdef
Answer: a
Explanation: “i” is not in “abcdef”
15. x = "abcdef"
i = "a"
while i in x:
print(i, end = " ")
a) no output
b) i i i i i i …
c) a a a a a a …
d) a b c d e f
Answer: c
Explanation: As the value of i or x isn’t changing, the condition will always evaluate to True.
16. x = "abcdef"
i = "a"
while i in x:
print('i', end = " ")
a) no output
b) i i i i i i …
c) a a a a a a …
d) a b c d e f
Answer: b
Explanation: As the value of i or x isn’t changing, the condition will always evaluate to True.
17. x = "abcdef"
i = "a"
while i in x:
x = x[:-1]
print(i, end = " ")
a) i i i i i i
b) a a a a a a
c) a a a a a
d) none of the mentioned
Answer: b
Explanation: The string x is being shortened by one character in each iteration.
18. x = "abcdef"
i = "a"
while i in x[:-1]:
print(i, end = " ")
a) a a a a a
b) a a a a a a
c) a a a a a a …
d) a
Answer: c
Explanation: String x is not being altered and i is in x[:-1]
19. x = "abcdef"
i = "a"
while i in x:
x = x[1:]
print(i, end = " ")
a) a a a a a a
b) a
c) no output
d) error
Answer: b
Explanation: The string x is being shortened by one character in each iteration.
20. x = "abcdef"
i = "a"
while i in x[1:]:
print(i, end = " ")
a) a a a a a a
b) a
c) no output
d) error
Answer: c
Explanation: i is not in x[1:].
21. x = 'abcd'
for i in x:
print(i)
x.upper()
a) a B C D
b) a b c d
c) A B C D
d) error
Answer: b
Explanation: Changes do not happen in-place, rather a new instance of the string is returned.
22. x = 'abcd'
for i in x:
print(i.upper())
a) a b c d
b) A B C D
c) a B C D
d) error
Answer: b
Explanation: The instance of the string returned by upper() is being printed.
23. x = 'abcd'
for i in range(x):
print(i)
a) a b c d
b) 0 1 2 3
c) error
d) none of the mentioned
Answer: c
Explanation: range(str) is not allowed.
24. x = 'abcd'
for i in range(len(x)):
print(i)
a) a b c d
b) 0 1 2 3
c) error
d) 1 2 3 4
Answer: b
Explanation: i takes values 0, 1, 2 and 3.
25. x = 'abcd'
for i in range(len(x)):
print(i.upper())
a) a b c d
b) 0 1 2 3
c) error
d) 1 2 3 4
Answer: c
Explanation: Objects of type int have no attribute upper()
26. x = 'abcd'
for i in range(len(x)):
i.upper()
print (x)
a) a b c d
b) 0 1 2 3
c) error
d) none of the mentioned
Answer: c
Explanation: Objects of type int have no attribute upper().
27. x = 'abcd'
for i in range(len(x)):
i.upper()
print (x)
a) a b c d
b) 0 1 2 3
c) error
d) none of the mentioned
Answer: c
Explanation: Objects of type int have no attribute upper().
28. x = 'abcd'
for i in range(len(x)):
i[x].upper()
print (x)
a) abcd
b) ABCD
c) error
d) none of the mentioned
Answer: c
Explanation: Objects of type int aren’t subscriptable. However, if the statement was x[i],
an error would not have been thrown.
29. x = 'abcd'
for i in range(len(x)):
x = 'a'
print(x)
a) a
b) abcd abcd abcd
c) a a a a
d) none of the mentioned
Answer: c
Explanation: range() is computed only at the time of entering the loop.
30. x = 'abcd'
for i in range(len(x)):
print(x)
x = 'a'
a) a
b) abcd abcd abcd abcd
c) a a a a
d) none of the mentioned
Answer: d
Explanation: abcd a a a is the output as x is modified only after ‘abcd’ has been printed once.
31. x = 123
for i in x:
print(i)
a) 1 2 3
b) 123
c) error
d) none of the mentioned
Answer: c
Explanation: Objects of type int are not iterable.
32. d = {0: 'a', 1: 'b', 2: 'c'}
for i in d:
print(i)
a) 0 1 2
b) a b c
c) 0 a 1 b 2 c
d) none of the mentioned
Answer: a
Explanation: Loops over the keys of the dictionary.
33. d = {0: 'a', 1: 'b', 2: 'c'}
for x, y in d:
print(x, y)
a) 0 1 2
b) a b c
c) 0 a 1 b 2 c
d) none of the mentioned
Answer: d
Explanation: Error, objects of type int aren’t iterable.
34. d = {0: 'a', 1: 'b', 2: 'c'}
for x, y in d.items():
print(x, y)
a) 0 1 2
b) a b c
c) 0 a 1 b 2 c
d) none of the mentioned
Answer: c
Explanation: Loops over key, value pairs.
35. d = {0: 'a', 1: 'b', 2: 'c'}
for x in d.keys():
print(d[x])
a) 0 1 2
b) a b c
c) 0 a 1 b 2 c
d) none of the mentioned
Answer: b
Explanation: Loops over the keys and prints the values.
36. d = {0: 'a', 1: 'b', 2: 'c'}
for x in d.values():
print(x)
a) 0 1 2
b) a b c
c) 0 a 1 b 2 c
d) none of the mentioned
Answer: b
Explanation: Loops over the values.
37. d = {0: 'a', 1: 'b', 2: 'c'}
for x in d.values():
print(d[x])
a) 0 1 2
b) a b c
c) 0 a 1 b 2 c
d) none of the mentioned
Answer: d
Explanation: Causes a KeyError.
38. d = {0, 1, 2}
for x in d.values():
print(x)
a) 0 1 2
b) None None None
c) error
d) none of the mentioned
Answer: c
Explanation: Objects of type set have no attribute values.
39. d = {0, 1, 2}
for x in d:
print(x)
a) 0 1 2
b) {0, 1, 2} {0, 1, 2} {0, 1, 2}
c) error
d) none of the mentioned
Answer: a
Explanation: Loops over the elements of the set and prints them.
40. d = {0, 1, 2}
for x in d:
print(d.add(x))
a) 0 1 2
b) 0 1 2 0 1 2 0 1 2 …
c) None None None
d) None of the mentioned
Answer: c
Explanation: Variable x takes the values 0, 1 and 2. set.add() returns None which is printed.
41. What will be the output of the following Python code?
values = [[3, 4, 5, 1], [33, 6, 1, 2]]
v = values[0][0]
for row in range(0, len(values)):
for column in range(0, len(values[row])):
if v < values[row][column]:
v = values[row][column]
print(v)
a) 3
b) 5
c) 6
d) 33
Answer: d
Explanation: Execute in the shell to verify.
42. What will be the output of the following Python code?
values = [[3, 4, 5, 1], [33, 6, 1, 2]]
v = values[0][0]
for lst in values:
for element in lst:
if v > element:
v = element
print(v)
a) 1
b) 3
c) 5
d) 6
Answer: a
Explanation: Execute in the shell to verify.
43. What will be the output of the following Python code?
matrix = [[1, 2, 3, 4],
[4, 5, 6, 7],
[8, 9, 10, 11],
[12, 13, 14, 15]]
for i in range(0, 4):
print(matrix[i][1], end = " ")
a) 1 2 3 4
b) 4 5 6 7
c) 1 3 8 12
d) 2 5 9 13
Answer: d
Explanation: Execute in the shell to verify.
45. What will be the output of the following Python code?
values = [[3, 4, 5, 1 ], [33, 6, 1, 2]]
for row in values:
row.sort()
for element in row:
print(element, end = " ")
a) The program prints two rows 3 4 5 1 followed by 33 6 1 2
b) The program prints on row 3 4 5 1 33 6 1 2
c) The program prints two rows 3 4 5 1 followed by 33 6 1 2
d) The program prints two rows 1 3 4 5 followed by 1 2 6 33
Answer: d
Explanation: Execute in the shell to verify.
46. What will be the output of the following Python code?
a= [1, 2, 3, 4, 5]
for i in range(1, 5):
a[i-1] = a[i]
for i in range(0, 5):
print(a[i],end = " ")
a) 5 5 1 2 3
b) 5 1 2 3 4
c) 2 3 4 5 1
d) 2 3 4 5 5
Answer: d
Explanation: The items having indexes from 1 to 4 are shifted forward by one index due to
the first for-loop and the item of index four are printed again because of the second for-loop.
47. What will be the output of the following Python code?
num = ['One', 'Two', 'Three']
for i, x in enumerate(num):
print('{}: {}'.format(i, x),end=" ")
a) 1: 2: 3:
b) Exception is thrown
c) One Two Three
d) 0: One 1: Two 2: ThreeV
Answer: d
Explanation: enumerate(iterator,start=0) is a built-in function which returns (0,lst[0]),(1,lst[1])
and so on where lst is a list(iterator).
48. What will be the output of the following Python code?
a = [1, 5, 7, 9, 9, 1]
b = a[0] # b=1
x= 0
for x in range(1, len(a)): # for x in range(1, 6)
if a[x] > b:
b = a[x]
b = x
print(b)
a) 5
b) 3
c) 4
d) 0
Answer: c
Explanation: The above piece of code basically prints the index of the largest element in the list.
49. What will be the output of the following Python code snippet?
a={1:"A", 2:"B", 3:"C"}
for i,j in a.items():
print(i,j,end=" ")
a) 1 A 2 B 3 C
b) 1 2 3
c) A B C
d) 1:”A” 2:”B” 3:”C”
Answer: a
Explanation: In the above code, variables i and j iterate over the keys and values of the dictionary respectively
50. What will be the output of the following Python code?
a={1:"A",2:"B",3:"C"}
for i in a:
print(i,end=" ")
a) 1 2 3
b) ‘A’ ‘B’ ‘C’
c) 1 ‘A’ 2 ‘B’ 3 ‘C’
d) Error, it should be: for i in a.items():
Answer: a
Explanation: The variable I iterates over the keys of the dictionary and hence the keys are printed.
51. What will be the output of the following Python code snippet?
a = {}
a[1] = 1
a['1'] = 2
a[1]=a[1]+1
count = 0
for i in a:
count += a[i]
print(count)
a) 1
b) 2
c) 4
d) Error, the keys can’t be a mixture of letters and numbers
Answer: c
Explanation: The above piece of code basically finds the sum of the values of keys.
52. What will be the output of the following Python code snippet?
a = {}
a[1] = 1
a['1'] = 2
a[1.0]=4
count = 0
for i in a:
count += a[i]
print(count)
a) An exception is thrown
b) 3
c) 6
d) 2
Answer: c
Explanation: The value of key 1 is 4 since 1 and 1.0 are the same.
Then, the function count() gives the sum of all the values of the keys (2+4).
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