I want to add one more answer :
It happens when you try to pass positional parameter with wrong position order along with keyword argument in calling function.
there is difference between parameter and argument you can read in detail about here Arguments and Parameter in python
def hello(a,b=1, *args):
print(a, b, *args)
hello(1, 2, 3, 4,a=12)
since we have three parameters :
a is positional parameter
b=1 is keyword and default parameter
*args is variable length parameter
so we first assign a as positional parameter , means we have to provide value to positional argument in its position order, here order matter. but we are passing argument 1 at the place of a in calling function and then we are also providing value to a , treating as keyword argument. now a have two values :
one is positional value: a=1
second is keyworded value which is a=12
We have to change hello(1, 2, 3, 4,a=12) to hello(1, 2, 3, 4,12)
so now a will get only one positional value which is 1 and b will get value 2 and rest of values will get *args (variable length parameter)
if we want that *args should get 2,3,4 and a should get 1 and b should get 12
then we can do like this
def hello(a,*args,b=1):
pass
hello(1, 2, 3, 4,b=12)
Something more :
def hello(a,*c,b=1,**kwargs):
print(b)
print(c)
print(a)
print(kwargs)
hello(1,2,1,2,8,9,c=12)
output :
1
(2, 1, 2, 8, 9)
1
{'c': 12}