Let's show the cardinal parameters of a function by a simple example, we will start by writing the simplest function
def test(*args,**kwargs): print(args,kwargs)
Then define two variables
l = [1,2,3,4]
d = {"a":1,"b":2}
Let's look at the differences between each of the two ways of passing a parameter.
The first way
test(l,d)
If you are using the above method of passing a parameter, then the 2 variables l and d are passed to args, a formal parameter, as the two elements of the args variable, and kwargs is an empty dictionary without any parameters to pass a he
([1, 2, 3, 4], {'a': 1, 'b': 2}) {}
We can see that the list l and the dictionary d are treated as two elements of a tuple
The second way
test(*l,**d)
If the parameter is passed in the above way, then the variable l will be assigned to args and the variable d will be assigned to kwargs
(1, 2, 3, 4) {'a': 1, 'b': 2}
Through the above demonstration, you should basically understand python's universal parameters, and know how you should pass parameters if the function uses universal parameters.
Got confused today and combed through the universal parameters again
Let's take a look at this function
def foo(action=None,**kwargs):
print("action",action,sep="=================>")
print("kwargs", kwargs, sep="=================>")
d = {"a":1,"b":2}
foo(d)
print("=".center(100,"*"))
foo(**d)
The result of my implementation is as follows
Let me explain.
The first way to call a function, a dictionary is passed in, which is passed in as a whole, and this dictionary is assigned to the position change, which is the action
The second way to call the function, passing it in via the **dictionary method, he actually passes it in like this a=1, b=2 so it's actually a named variable, and the names of these 2 variables don't ACTION, so the result of the second way to call it would be
action is none
kwargs is a dictionary
Let's take a look at the third method of invocation
d = {"action":"action","a":1}
foo(**d)
Here's a look at the results to see if it makes a little more sense
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