The cmath.asin() function computes the arc sine of a given value. The  input value maybe real or complex but the return value will always be complex.

x The value(real or complex) whose arc sine we want.

The function returns the arc cosine of x in radians as a complex number. If the given input value is a real number, the returned complex value will have 0j as its imaginary part.

import cmath
print(cmath.asin(1 + 2j))
print(cmath.asin(0.5 + 1.2j))

You should note that the cmath(complex math) is an extension of the popular math module. It is made to work primarily with complex numbers. If you are working with real numbers the math.asin() maybe more relevant.