# test.pyx
class Foo:
    def __init__(self, x, y):
        self.x = x
        self.y = y

# test2.py
import pyximport
pyximport.install()
import test
foo = test.Foo(1, 2)
print foo.x, foo.y

# % python2.7 test2.py
# Traceback (most recent call last):
#   File "test2.py", line 4, in <module>
#     foo = test.Foo(1, 2)
# AttributeError: 'module' object has no attribute 'Foo'