Finding the real cube root of a number in Python
There is a unique real cube root of every real number.
For example, 5 is a real cube root of 125 because we can write 125 as the product of 3 positive 5's.
In Python, however, when it comes to finding a real cube root of a negative number n, simply raising n to the power of 1/3 results in a complex number.
For example, either pow(-125, (1/3)) or (-125) ** (1/3) evaluates to (2.5+4.330127018922192j) instead of -5.
In this kata, you are going to come up with a function that correctly calculates a real cube root of an input number, which can be zero, a positive real number or a negative one.
test.assert_equals( real_cube_root( 0 ), 0 ) test.assert_equals( real_cube_root( 5 ), 5 ** (1 / 3) ) test.assert_equals( real_cube_root( -5 ), -5 ** (1 / 3) ) test.assert_equals( real_cube_root( -50 ), -50 ** (1 / 3) ) test.assert_equals( real_cube_root( -105 ), -105 ** (1 / 3) )- test.assert_equals( real_cube_root( 0 ), 0 )
- test.assert_equals( real_cube_root( 5 ), 5 ** (1 / 3) )
- test.assert_equals( real_cube_root( -5 ), -5 ** (1 / 3) )
- test.assert_equals( real_cube_root( -50 ), -50 ** (1 / 3) )
- test.assert_equals( real_cube_root( -105 ), -105 ** (1 / 3) )
There is a unique real cube root of every real number.
For example, 5 is a real cube root of 125 because we can write 125 as the product of 3 positive 5's.
In Python, however, when it comes to finding a real cube root of a negative number n, simply raising n to the power of 1/3 results in a complex number.
For example, either pow(-125, (1/3)) or (-125) ** (1/3) evaluates to (2.5+4.330127018922192j) instead of -5.
In this kata, you are going to come up with a function that correctly calculates a real cube root of an input number, which can be zero, a positive real number or a negative one.
def real_cube_root(n):
if n >= 0: return n ** (1/3)
else: return -abs(n ** (1/3))