interface.py

# compose a graph of nodes

x = Variable(10.01)
y = Variable(0.05)

z = x * y
m = 1.3
q = m+y

L = (q - (z**(m/2.) + z**2. - 1./z))**2

# the forward calculation
print(L.value)

# the backward calculation
L.backward()

# gradients of the inputs are updated
print('x: {} \ny: {}'.format(x.gradient, y.gradient))

# clear gradients if we don't want to accumulate on next backward()
# will follow tree down to clear gradient of x,y as well
L.clear_gradient()