# Python Questions and Answers – Math – 2

This set of Python Developer Questions & Answers focuses on “Mathematical Functions”.

1. What does the function math.frexp(x) return?
a) a tuple containing the mantissa and the exponent of x
b) a list containing the mantissa and the exponent of x
c) a tuple containing the mantissa of x
d) a list containing the exponent of x

Explanation: It returns a tuple with two elements. The first element is the mantissa and the second element is the exponent.

2. What is the result of math.fsum([.1 for i in range(20)])?
a) 2.0
b) 20
c) 2
d) 2.0000000000000004

Explanation: The function fsum returns an accurate floating point sum of the elements of its argument.

3. What is the result of sum([.1 for i in range(20)])?
a) 2.0
b) 20
c) 2
d) 2.0000000000000004

Explanation: There is some loss of accuracy when we use sum with floating point numbers. Hence the function fsum is preferable.

4. What is returned by math.isfinite(float(‘inf’))?
a) True
b) False
c) None
d) error

Explanation: float(‘inf’) is not a finite number.

5. What is returned by math.isfinite(float(‘nan’))?
a) True
b) False
c) None
d) error

Explanation: float(‘nan’) is not a finite number.

6. What is x if x = math.isfinite(float(‘0.0’))?
a) True
b) False
c) None
d) error

Explanation: float(‘0.0’) is a finite number.

7. What will be the output of the following Python code?

>>> -float('inf') + float('inf')

a) inf
b) nan
c) 0
d) 0.0

Explanation: The result of float(‘inf’)-float(‘inf’) is undefined.

8. What will be the output of the following Python code?

print(math.isinf(float('-inf')))

a) error, the minus sign shouldn’t have been inside the brackets
b) error, there is no function called isinf
c) True
d) False

Explanation: -float(‘inf’) is the same as float(‘-inf’).

9. What is the value of x if x = math.ldexp(0.5, 1)?
a) 1
b) 2.0
c) 0.5
d) none of the mentioned

Explanation: The value returned by ldexp(x, y) is x * (2 ** y). In the current case x is 1.0.

10. What is returned by math.modf(1.0)?
a) (0.0, 1.0)
b) (1.0, 0.0)
c) (0.5, 1)
d) (0.5, 1.0)

Explanation: The first element is the fractional part and the second element is the integral part of the argument.

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