I tried using doctest

doctest library

Immediately after the function definition, you can put something like '''foo bar buzz''' in python to describe the function. This is called docstring. doctest is talking about using this docstring to test the operation of functions.

I tried using it

Overview

I have to write some function. I chose fizzbuzz because it's too normal like factorial. There is a binding called ʻone liner` in python, and I tried using the code here.

`fizzbuzz.py`


def fizzbuzz(n):
    """
    This function returns a list whose elements are
    converted into fizzbuzz form.

    >>> fizzbuzz(10)
    [1, 2, 'Fizz', 4, 'Buzz', 'Fizz', 7, 8, 'Fizz', 'Buzz']
    >>> len(fizzbuzz(9))
    9
    >>> fizzbuzz(10) + 1
    Traceback (most recent call last):
      File "/Users/yourname/python/fizbuzz.py", line 32, in <module>
        fizzbuzz(10) + 1
    TypeError: can only concatenate list (not "int") to list
    """
    for i in range(1,n+1): res.append("FizzBuzz"[(i**2)%3*4:8--(i**4)%5] or i)
    return res


if __name__ == '__main__':
    import doctest
    doctest.testmod()

About the FizzBuzz function

To explain a little, the character string "FizzBuzz" is cut and printed. The desired string is cut out by adjusting the number on the left and right separated by :. in short

case(i):
i is[Multiple of 3]And[Multiple of 5]:
    "FizzBuzz"[0:8]

i is[Multiple of 3]And[Not a multiple of 5]:
    "FizzBuzz"[0:4]

i is[Not a multiple of 3]And[Multiple of 5]:
    "FizzBuzz"[4:8]

i is[Not a multiple of 3]And[Not a multiple of 5]:
    "FizzBuzz"[4:4] /* Empty String => None */

That is. To achieve this, prepare 0 for multiples of 3, 4 for others, 8 for multiples of 5, and 4 for others. Since it's a one-liner, I'm trying hard with the surplus, but I think it's okay to create a separate function.

Impressions

This happens when an error occurs

By the way, I simulated it when I increased the value to be returned.

**********************************************************************
File "/Users/hiroberry/python/foo.py", line 8, in __main__.fizzbuzz
Failed example:
    len(fizzbuzz(9))
Expected:
    10
Got:
    9
**********************************************************************
1 items had failures:
   1 of   3 in __main__.fizzbuzz
***Test Failed*** 1 failures.
[Finished in 0.1s]

It's obvious at a glance. It would be too convenient.

About Traceback

I made a special example that doesn't work and tried it. Traceback The following statements don't seem to have to match exactly. Apparently, I'm only looking at the statement TypeError: can only ....