Testing floating point equality

Is there a function to test floating point approximate equality in python? Something like,

 def approx_equal(a, b, tol):
     return abs(a - b) < tol

My use case is similar to how Google's C++ testing library, gtest.h, defines EXPECT_NEAR.

Here is an example:

def bernoulli_fraction_to_angle(fraction):
    return math.asin(sqrt(fraction))
def bernoulli_angle_to_fraction(angle):
    return math.sin(angle) ** 2
def test_bernoulli_conversions():
    assert(approx_equal(bernoulli_angle_to_fraction(pi / 4), 0.5, 1e-4))
    assert(approx_equal(
              bernoulli_fraction_to_angle(bernoulli_angle_to_fraction(0.1)),
                0.1, 1e-4))