Python Multiple Choice Questions on “Numeric Types”.
1. What is the output of print 0.1 + 0.2 == 0.3?
a) True
b) False
c) Machine dependent
d) Error
Answer: b
Clarification: Neither of 0.1, 0.2 and 0.3 can be represented accurately in binary. The round off errors from 0.1 and 0.2 accumulate and hence there is a difference of 5.5511e-17 between (0.1 + 0.2) and 0.3.
2. Which of the following is not a complex number?
a) k = 2 + 3j
b) k = complex(2, 3)
c) k = 2 + 3l
d) k = 2 + 3J
Answer: c
Clarification: l (or L) stands for long.
3. What is the type of inf?
a) Boolean
b) Integer
c) Float
d) Complex
Answer: c
Clarification: Infinity is a special case of floating point numbers. It can be obtained by float(‘inf’).
4. What does ~4 evaluate to?
a) -5
b) -4
c) -3
d) +3
Answer: a
Clarification: ~x is equivalent to -(x+1).
5. What does ~~~~~~5 evaluate to?
a) +5
b) -11
c) +11
d) -5
Answer: a
Clarification: ~x is equivalent to -(x+1).
~~x = – (-(x+1) + 1) = (x+1) – 1 = x
~~x is equivalent to x
Extrapolating further ~~~~~~x would be same as x in the final result.
In the question, x value is given as 5 and “~” is repeated 6 times. So, the correct answer for “~~~~~~5” is 5.
6. Which of the following is incorrect?
a) x = 0b101
b) x = 0x4f5
c) x = 19023
d) x = 03964
Answer: d
Clarification: Numbers starting with a 0 are octal numbers but 9 isn’t allowed in octal numbers.
7. What is the result of cmp(3, 1)?
a) 1
b) 0
c) True
d) False
Answer: a
Clarification: cmp(x, y) returns 1 if x > y, 0 if x == y and -1 if x < y.
8. Which of the following is incorrect?
a) float(‘inf’)
b) float(‘nan’)
c) float(’56’+’78’)
d) float(’12+34′)
Answer: d
Clarification: ‘+’ cannot be converted to a float.
9. What is the result of round(0.5) – round(-0.5)?
a) 1.0
b) 2.0
c) 0.0
d) Value depends on Python version
Answer: d
Clarification: The behavior of the round() function is different in Python 2 and Python 3. In Python 2, it rounds off numbers away from 0 when the number to be rounded off is exactly halfway through. round(0.5) is 1 and round(-0.5) is -1 whereas in Python 3, it rounds off numbers towards nearest even number when the number to be rounded off is exactly halfway through. See the below output.
Here’s the runtime output for Python version 2.7 interpreter.
$ python Python 2.7.17 (default, Nov 7 2019, 10:07:09) >>> round(0.5) 1.0 >>> round(-0.5) -1.0 >>>
In the above output, you can see that the round() functions on 0.5 and -0.5 are moving away from 0 and hence “round(0.5) – (round(-0.5)) = 1 – (-1) = 2”
Here’s the runtime output for Python version 3.6 interpreter.
$ python3 Python 3.6.8 (default, Oct 7 2019, 12:59:55) >>> round(0.5) 0 >>> round(-0.5) 0 >>> round(2.5) 2 >>> round(3.5) 4 >>>
In the above output, you can see that the round() functions on 0.5 and -0.5 are moving towards 0 and hence “round(0.5) – (round(-0.5)) = 0 – 0 = 0“. Also note that the round(2.5) is 2 (which is an even number) whereas round(3.5) is 4 (which is an even number).
10. What does 3 ^ 4 evaluate to?
a) 81
b) 12
c) 0.75
d) 7
Answer: d
Clarification: ^ is the Binary XOR operator.