I'm trying to pass a string argument to a target function in a process. Somehow, the string is interpreted as a list of as many arguments as there are characters.
This is the code:
p = multiprocessing.Process(target=write, args=('hello'))
Traceback (most recent call last):
>>> File "/usr/local/lib/python2.5/site-packages/multiprocessing/process.py", line 237, in _bootstrap
File "/usr/local/lib/python2.5/site-packages/multiprocessing/process.py", line 93, in run
TypeError: write() takes exactly 1 argument (5 given)
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".