I think 'unpack' might be the wrong vocabulary here - apologies because I'm sure this is a duplicate question.
My question is pretty simple: in a function that expects a list of items, how can I pass a Python list item without getting an error?
my_list = ['red', 'blue', 'orange']
function_that_needs_strings('red', 'blue', 'orange') # works!
function_that_needs_strings(my_list) # breaks!
Surely there must be a way to expand the list, and pass the function 'red','blue','orange' on the hoof?
Yes, you can use the *args (splat) syntax:
function_that_needs_strings(*my_list)
where my_list can be any iterable; Python will loop over the given object and use each element as a separate argument to the function.
See the call expression documentation.
There is a keyword-parameter equivalent as well, using two stars:
kwargs = {'foo': 'bar', 'spam': 'ham'}
f(**kwargs)
and there is equivalent syntax for specifying catch-all arguments in a function signature:
def func(*args, **kw):
# args now holds positional arguments, kw keyword arguments
Since Python 3.5 you can unpack unlimited amount of lists.
PEP 448 - Additional Unpacking Generalizations
So this will work:
a = ['1', '2', '3', '4']
b = ['5', '6']
function_that_needs_strings(*a, *b)
