>>> from p2 import inventory

>>> stock = {'SPAGHETTI': 30, 'RAVIOLI': 20, 'MACARONI': 3}
>>> r = inventory(stock, 'registration.txt', 'soldout.txt')
>>> print(r)
None
>>> if (stock != {'SPAGHETTI': 50, 'RAVIOLI': 0, 'MACARONI': -2}):
...     print(stock)
>>> with open('soldout.txt', 'r') as out:
...     data = out.readlines()
>>> sorted(data)
['MACARONI\n', 'RAVIOLI\n']

>>> lf =['IN RAVIOLI 10', 'OUT SPAGHETTI 50', 'IN MACARONI 70', 'OUT SPAGHETTI 20',
...      'OUT RAVIOLI 50', 'IN SPAGHETTI 60', 'OUT MACARONI 90', 'IN RAVIOLI 15']
>>> with open('example.txt', 'w') as f:
...    for e in lf:
...        a = f.write(e+'\n')

>>> stock1 = {'SPAGHETTI': 10, 'RAVIOLI': 10, 'MACARONI': 50}
>>> r = inventory(stock1, 'example.txt', 'soldout1.txt')
>>> print(r)
None
>>> if (stock1 != {'SPAGHETTI': 0, 'RAVIOLI': -15, 'MACARONI': 30}):
...     print(stock1)
>>> with open('soldout1.txt', 'r') as out:
...     data = out.readlines()
>>> sorted(data)
['RAVIOLI\n', 'SPAGHETTI\n']

>>> stock2 = {'SPAGHETTI': 5, 'RAVIOLI': 70, 'MACARONI': 20}
>>> r = inventory(stock2, 'example.txt', 'soldout2.txt')
>>> print(r)
None
>>> if (stock2 != {'SPAGHETTI': -5, 'RAVIOLI': 45, 'MACARONI': 0}):
...     print(stock2)
>>> with open('soldout2.txt', 'r') as out:
...     data = out.readlines()
>>> sorted(data)
['MACARONI\n', 'SPAGHETTI\n']

>>> stock3 = {'SPAGHETTI': 10, 'RAVIOLI': 50, 'MACARONI': 95}
>>> r = inventory(stock3, 'example.txt', 'soldout3.txt')
>>> print(r)
None
>>> if (stock3 != {'SPAGHETTI': 0, 'RAVIOLI': 25, 'MACARONI': 75}):
...     print(stock3)
>>> with open('soldout3.txt', 'r') as out:
...     data = out.readlines()
>>> sorted(data)
['SPAGHETTI\n']