You can actually do this:
std::map<std::string, int> mymap = {{"one", 1}, {"two", 2}, {"three", 3}};
What is actually happening here is that std::map stores an std::pair of the key value types, in this case std::pair<const std::string,int>. This is only possible because of c++11’s new uniform initialization syntax which in this case calls a constructor overload of std::pair<const std::string,int>. In this case std::map has a constructor with an std::intializer_list which is responsible for the outside braces.
So unlike python’s any class you create can use this syntax to initialize itself as long as you create a constructor that takes an initializer list (or uniform initialization syntax is applicable)