This feels like a bug to me. I am unable to replace a character in a string with a single backslash:
>>>st = "a&b"
>>>st.replace('&','\\')
'a\\b'
I know that '\' isn't a legitimate string because the \ escapes the last '.
However, I don't want the result to be 'a\\b'; I want it to be 'a\b'. How is this possible?
You are looking at the string representation, which is itself a valid Python string literal.
The \\ is itself just one slash, but displayed as an escaped character to make the value a valid Python literal string. You can copy and paste that string back into Python and it'll produce the same value.
Use print st.replace('&','\\') to see the actual value being displayed, or test for the length of the resulting value:
>>> st = "a&b"
>>> print st.replace('&','\\')
a\b
>>> len(st.replace('&','\\'))
3
