Mock vs MagicMock

What is the reason for plain Mock existing?

Mock's author, Michael Foord, addressed a very similar question at Pycon 2011 (31:00):

Q: Why was MagicMock made a separate thing rather than just folding the ability into the default mock object?

A: One reasonable answer is that the way MagicMock works is that it preconfigures all these protocol methods by creating new Mocks and setting them, so if every new mock created a bunch of new mocks and set those as protocol methods and then all of those protocol methods created a bunch more mocks and set them on their protocol methods, you've got infinite recursion...

What if you want accessing your mock as a container object to be an error -- you don't want that to work? If every mock has automatically got every protocol method, then it becomes much more difficult to do that. And also, MagicMock does some of this preconfiguring for you, setting return values that might not be appropriate, so I thought it would be better to have this convenience one that has everything preconfigured and available for you, but you can also take a ordinary mock object and just configure the magic methods you want to exist...

The simple answer is: just use MagicMock everywhere if that's the behavior you want.

With Mock you can mock magic methods but you have to define them. MagicMock has "default implementations of most of the magic methods.".

If you don't need to test any magic methods, Mock is adequate and doesn't bring a lot of extraneous things into your tests. If you need to test a lot of magic methods MagicMock will save you some time.