Return multiple items from a mocked function with Python's mock.

gistfile1.py

import mock

def returnList(items):
  def func():
    for item in items:
      yield item
    yield mock.DEFAULT

  generator = func()

  def effect(*args, **kwargs):
    return generator.next()

  return effect


m = mock.Mock()
m.side_effect = returnList([1,2,3])
for i in ['a', 'b', 'c']:
    print i, m()

It is also possible to do the same using the code below:

return_values = [1,2,3]
call_values = [1,2,3]

m2 = mock.Mock()
m2.side_effect = lambda: return_values.pop()
m2.return_value = lambda: call_values.pop()
for i in ['a', 'b', 'c']:
    print i, m2(), m2.return_value()

another way of doing the same thing

return_values = [1,2,3]

def f():
    m2.return_value = return_values[m2.call_count-1]
    return return_values[m2.call_count-1]

m2 = mock.Mock()
m2.side_effect = f

for i in ['a', 'b', 'c']:
    print i, m2(), m2.return_value

Your main example rewritten to be Python 2 and 3 compatible:

try:
    import mock
except ImportError:
    import unittest.mock as mock


def return_list(items):
    def func():
        for item in items:
            yield item
        yield mock.DEFAULT

    generator = func()

    def effect(*args, **kwargs):
        return next(generator)

    return effect


m = mock.Mock()
m.side_effect = return_list([1, 2, 3])
for i in ['a', 'b', 'c']:
    print(i, m())

Thanks for this gist, vpetro! Very helpful. You can use iter to simplify a bit:

try:
    import mock
except ImportError:
    import unittest.mock as mock


def return_list(items):
    def func():
        return iter(items)

    generator = func()

    def effect(*args, **kwargs):
        return next(generator)

    return effect


m = mock.Mock()
m.side_effect = return_list([1, 2, 3]) 
for i in ['a', 'b', 'c']:
    print(i, m())

Turns out you can also just set a side effect to any iterable, including a list:

m = mock.Mock()
m.side_effect = [1, 2, 3]
for i in ['a', 'b', 'c']:
    print(i, m())

http://stackoverflow.com/questions/24897145/python-mock-multiple-return-values

Thanks for your great ideas, vpetro.
By the way, you can always use return_values.pop instead of lambda: return_values.pop().