pickle_std_string_vector.C

#import <iostream>
#import <TPython.h>
#import <TString.h>
#import <vector>
#import <string>

Int_t pickle_std_string_vector(std::vector<std::string> string_vec = { "foo", "bar"}, std::string pickle_filename = "tmp.p") {
  TPython p = TPython();
  p.Exec("import pickle");
  p.Exec("list_to_pickle = []");
  for(std::string& i: string_vec) {
    p.Exec((std::string("list_to_pickle.append(\"")+i+std::string("\")")).c_str());
  }
  p.Exec((std::string("pickle.dump(list_to_pickle, open(\"")+pickle_filename+std::string("\", \"w\"))")).c_str());

  return 0;
}
    
std::vector<std::string> unpickle_std_string_vector(std::string pickle_filename = "tmp.p") {
  TPython p = TPython();
  p.Exec("import pickle");
  p.Exec((std::string("unpickled_list = pickle.load(open(\"")+pickle_filename+std::string("\", \"r\"))")).c_str());
  p.Exec("return_vector_py = ROOT.std.vector(\"std::string\")()");
  p.Exec(std::string("for i in unpickled_list: return_vector_py.push_back(i)").c_str());
  TPyReturn pyReturn = p.Eval("return_vector_py");
  std::vector<std::string> * _ = (std::vector<std::string> *)(void *)pyReturn;

  std::vector<std::string> return_vector = *_;
  return return_vector;
}

(For use with ROOT 6, load as a macro.)

This could do with templating to pickle anything, however creating objects into python could be tricky. Could be solved by using a std::string for the ROOT class and a std::string for the python class in the arguments of the function.