I found a useful method called 'read_dict' that solved the problem.

from configparser import ConfigParser
from sys import stdout

structured_dict = dict(section1=dict(option1=1, option2=2, option3=3))
config = ConfigParser()
config.read_dict(structured_dict)
config.write(stdout)

# It writes this result in stdout as I expected:
# [section1]
# option1 = 1
# option2 = 2
# option3 = 3