Python Questions and Answers – While and For Loops – 3

This set of Tough Python Questions & Answers focuses on “While and For Loops”.

1. What is the output of the following?

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
View Answer

Answer: b
Explanation: Changes do not happen in-place, rather a new instance of the string is returned.

2. What is the output of the following?

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
View Answer

Answer: b
Explanation: The instance of the string returned by upper() is being printed.

3. What is the output of the following?

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
View Answer

Answer: c
Explanation: range(str) is not allowed.

4. What is the output of the following?

x = 'abcd'
for i in range(len(x)):
    print(i)

a) a b c d
b) 0 1 2 3
c) error
d) none of the mentioned
View Answer

Answer: b
Explanation: i takes values 0, 1, 2 and 3.

5. What is the output of the following?

x = 'abcd'
for i in range(len(x)):
    print(i.upper())

a) a b c d
b) 0 1 2 3
c) error
d) none of the mentioned
View Answer

Answer: c
Explanation: Objects of type int have no attribute upper().

6. What is the output of the following?

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
View Answer

Answer: c
Explanation: Objects of type int have no attribute upper().

7. What is the output of the following?

x = 'abcd'
for i in range(len(x)):
    x[i].upper()
print (x)

a) abcd
b) ABCD
c) error
d) none of the mentioned
View Answer

Answer: a
Explanation: Changes do not happen in-place, rather a new instance of the string is returned.

8. What is the output of the following?

x = 'abcd'
for i in range(len(x)):
    i[x].upper()
print (x)

a) abcd
b) ABCD
c) error
d) none of the mentioned
View Answer

Answer: c
Explanation: Objects of type int aren’t subscriptable.

9. What is the output of the following?

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
View Answer

Answer: c
Explanation: range() is computed only at the time of entering the loop.

10. What is the output of the following?

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
View Answer

Answer: d
Explanation: abcd a a a is the output as x is modified only after ‘abcd’ has been printed once.