C++ Cython Map operations returns {b'a': 2} rather than {'a': 2}

Question

Why does the following code print {b'a': 2} rather than {'a': 2}. And how can I fix it:

File1: parameters.pyx

# parameters.pyx
from libcpp.map cimport map
from libcpp.string  cimport string

cdef class Parameters:
    cdef map[string,int] data
    cdef int myVal

    def __init__(self):
        self.data['a'] = 1
        self.myVal = 0

    cpdef void change_data(self, map[string,int] newdata):
        self.data = newdata

    cpdef map[string,int] print_data(self):
        print(self.data)

    cpdef void change_myVal(self):
        self.myVal = 3

File2

# model.pyx

#from parameters import Parameters
from parameters import Parameters
from libcpp.map cimport map
from libcpp.string  cimport string

cpdef single_run():
    parameters = Parameters()

    cdef map[string,int] newMap
    
    newMap['a'] = 2

    parameters.change_data(newMap)

    
    parameters.print_data()

    parameters.change_myVal()

Setup.py file

#!/usr/bin/env python3

from setuptools import setup
from Cython.Build import cythonize

setup(
    ext_modules=cythonize(["*.py","*.pyx"],
language="c++")
    
)

Answer 1

You can directly use :

d = {b'a': 2}

as the b'a' is a byte object.

If you want to convert it into string you can use decode("utf-8") on byte object:

d = {k.decode("utf-8"):v for k,v in d.items()}

print(d)

#output
{'a': 2}