The result:

Latin

text_string = ''.join([chr(i) for i in range(ord(u'\u0021'), ord(u'\u007E') + 1)])
bpy.ops.font.text_insert(text=text_string)

Cyrilic

text_string = ''.join([chr(i) for i in range(ord(u'\u0410'), ord(u'\u044F') + 1)])
bpy.ops.font.text_insert(text=text_string)