That's because std::string does not carry any sort of encoding information, std::string is basically a wrapper around bytes (hopefully I'm not misreading this, I'm far from an expert C/C++ programmer). Due to this, python can't make any assumptions about encoding/decoding without the possibility of getting it wrong.

"Note that this class handles bytes independently of the encoding used: If used to handle sequences of multi-byte or variable-length characters (such as UTF-8), all members of this class (such as length or size), as well as its iterators, will still operate in terms of bytes (not actual encoded characters)."

https://stackoverflow.com/questions/1010783/what-encoding-do...

http://www.cplusplus.com/reference/string/string/