Turn python dict into a key=value string and back again

I'm currently refactoring a script that tags AWS resources and I came up with this one liner to generate pretty output. It basically turns {'tag1':'value1','tag2':'value2'} into tag1=value1, tag2=value2. Here is the code:

', '.join(['='.join(key_value) for key_value in {'a':'1','b':'2'}.items() ])

Oh, and if you like this, here is a function with additional functionality and protection:

def dict_to_key_value(data, sep='=', pair_sep=', '):
    """turns {'tag1':'value1','tag2':'value2'} into tag1=value1, tag2=value2"""
    return pair_sep.join([sep.join((unicode(key), unicode(value))) for key, value in data.items()])

Careful, this might blow up on dictionaries that nest other objects. Also here is a test:

def test_dict_to_key_value():
    data = {'tag1':'value1','tag2':'value2'}
    pretty_str = dict_to_key_value(data)
    assert('tag1=value1' in pretty_str)
    assert('tag2=value2' in pretty_str)
    assert('tag1=value1, tag2=value2' in pretty_str)
    not_as_pretty = dict_to_key_value(data,'x','x')
    assert('tag1xvalue1xtag2xvalue2' in not_as_pretty)

Here is the inverse, taking a list of key_value strings and returning a dictionary of the data:

def key_value_to_dict(key_value_list, sep='=', pair_sep=',' ):
    """
    Accept a key_value_list, like::

      key_value_list = ['a=1,b=2', 'c=3, d=4', 'e=5']

    Return a dict, like::

      {'a':'1', 'b':'2', 'c':'3', 'd':'4', 'e':'5'}
    """
    d = {}
    for speclist in key_value_list:
        for spec in speclist.strip().split(','):
            key, value = spec.strip().split('=')
            d[key] = value
    return d

And of course a test to prove it works how we expect:

def test_key_value_to_dict():
    key_value_list = ['a=1,b=2', 'c=3, d=4', 'e=5']
    desired_result = {'a':'1', 'b':'2', 'c':'3', 'd':'4', 'e':'5'}
    assert(key_value_to_dict(key_value_list) == desired_result)