As the error message say, you can't add int object to str object.
>>> 'str' + 2
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Can't convert 'int' object to str implicitly
Explicitly convert int object to str object, then concatenate:
>>> 'str' + str(2)
'str2'
Or use str.format
method:
>>> 'The answer is {}'.format(3)
'The answer is 3'