def function(a, b):
# description and test
"""Adds an integer and a float and returns a str.
>>> function(1, 3.0)
'4.0'
"""
# precondition
assert isinstance(a, int), 'a argument should be int'
assert isinstance(b, float), 'b argument should be float'
#implementation
try:
c = str(a + b)
return c
# postcondition
finally:
assert isinstance(c, str), 'c variable should be str'
# run all docstring test on debug mode
if __debug__:
import doctest
doctest.testmod()
if __name__ == '__main__':
# do something
pass