Create a mock "open" that will mock open multiple files in sequence

multi_mock_open.py

from unittest.mock import mock_open


def multi_mock_open(*file_contents):
    """Create a mock "open" that will mock open multiple files in sequence

    Args:
        *file_contents ([str]): a list of file contents to be returned by open

    Returns:
        (MagicMock) a mock opener that will return the contents of the first
            file when opened the first time, the second file when opened the
            second time, etc.
    """
    mock_files = [mock_open(read_data=content).return_value for content in file_contents]
    mock_opener = mock_open()
    mock_opener.side_effect = mock_files
    
    return mock_opener
  

Thanks, this was useful. I eventually came up with this:

builtin_open = open

def mapped_mock_open(file_contents_dict):
    """Create a mock "open" that will mock open multiple files based on name
    Args:
        file_contents_dict: A dict of 'fname': 'content'
    Returns:
        A Mock opener that will return the supplied content if name is in
        file_contents_dict, otherwise the builtin open
    """
    mock_files = {}
    for fname, content in file_contents_dict.items():
        mock_files[fname] = mock_open(read_data=content).return_value

    def my_open(fname, *args, **kwargs):
        if fname in mock_files:
            return mock_files[fname]
        else:
            return builtin_open(fname, *args, **kwargs)

    mock_opener = mock.Mock()
    mock_opener.side_effect = my_open
    return mock_opener

Great!

Thanks!