one_yield.py

In [35]: def a():
    a = yield 4
    print a
   ....:

In [36]: b = a()

In [37]: b.next()
Out[37]: 4

In [38]: b.send(2)
2

two_yields.py

In [30]: def a():
    yield 4
    x = yield
    print x
   ....:

In [31]: b = a()

In [32]: b.next()
Out[32]: 4

In [33]: b.next()

In [34]: b.send(2)
2