This is a common gotcha in Python – if you want to have a tuple with only one element, you need to specify that it’s actually a tuple (and not just something with brackets around it) – this is done by adding a comma after the element.
To fix this, just put a comma after the string, inside the brackets:
p = multiprocessing.Process(target=write, args=('hello',))
That way, Python will recognise it as a tuple with a single element, as intended. Currently, Python is interpreting your code as just a string. However, it’s failing in this particular way because a string is effectively list of characters. So Python is thinking that you want to pass (‘h’, ‘e’, ‘l’, ‘l’, ‘o’). That’s why it’s saying “you gave me 5 parameters”.