Escape double quotes for JSON in Python

How can I replace double quotes with a backslash and double quotes in Python?

>>> s = 'my string with "double quotes" blablabla'
>>> s.replace('"', '\\"')
'my string with \\"double quotes\\" blablabla'
>>> s.replace('"', '\\\"')
'my string with \\"double quotes\\" blablabla'

I would like to get the following:

'my string with \"double quotes\" blablabla'