def func(*items):
print(type(items))
a=list(items)
print(type(a))
a[3]= 1026
for i in a:
print i
items=[1,3,7,9,-99,555,88]
func(*items[:]) I am trying to pass a list into *args(*items) and it insists on unpacking it into a tuple, whose immutability makes manipulation of data nigh impossible without converting it into a list.
In all examples I see the default usage of *args is to print, or do some things fairly useless. Being new, I might have overlooked something blazingly obvious - which is why I put this question here:
Is conversion to tuple in *args functions default behaviour for list(array) arguments?
And is there a simple way to call variable arguments and have them default to mutable data types? A decorator?
millpond Wrote:Is conversion to tuple in *args functions default behaviour
Yes python always uses a tuple for the arguments in a function call. If you want a list, just add a line
def func(*items):
items = list(items)
...
Thank you for confirming that suspicion.
I will inscribe:
def func(*items):
items = list(items)
With my biggest, thickest magic marker into my notebook.
In all the books and videos I have on teaching python this fundamental rule has not been mentioned, unless I was braindead while I glossed over it!
Its a critical one for me. For my purposes, tuples make little sense, as mutable lists(arrays) are one of the main purposes for me even bothering to learn python.
millpond Wrote:For my purposes, tuples make little sense
In that case, it may be preferable to use a single array argument, for example
def func(items, spam, eggs):
items[1] = 3.14
func([10, 11, 12], 'foo', 'bar')
the * args is used to pass a number of arguments. the *items is not the list you created below.
tutorial on *args **kwargs
If you want a list passed to your function then just pass a list:
def func(my_list):
my_list[3]= 1026
res= []
for i in my_list:
res.append(i)
return res
items=[1,3,7,9,-99,555,88]
new_item= func(items)
print(new_item)Output:
[1, 3, 7, 1026, -99, 555, 88]
if a list is not passed then it will throw an error.