Membership Challenge. Confused how functions recognize arguments. .

My python is a little bit rusty, and I haven't done the coding challenge, so I'm not sure exactly what was required, but I'll try to help.... I think the reason you're getting confused, is that the variable names and the arguments names were the same.

In this example, you declared two variables:

my_dict = {'apples': 1, 'bananas': 2, 'coconuts': 3}
my_list = ['apples', 'coconuts', 'grapes', 'strawberries']

The variable names don't really matter, they could have just as easily been something like:

fruity_dictionary = {'apples': 1, 'bananas': 2, 'coconuts': 3}
yummy_list = ['apples', 'coconuts', 'grapes', 'strawberries']

These variables are then passed to the function when the function is called. This isn't included in the code above, but is how it would be validated.

members(fruity_dictionary, yummy_list)

When you define a function that requires arguments, you need to give those arguments a name, just like with variables. An argument in a function definition is simply a placeholder for the variables that you pass to it. In this example, the argument names were:

def members(the_dict, the_list)

Again, they could have been named whatever you wanted, like:

def members(thing1, thing2)

OR, in your case

def members(my_dict, my_list)

It's better to have descriptive names so you can quickly understand what's going on, but the point is that it doesn't really matter.

Hopefully that sheds a bit of light for you.

I added to my answer a bit, but I'll clarify here:

A function is basically a block of code that you would want to use over and over again. Lets say that we want to write a function that adds two numbers together, and returns the result. This is how we might write it:

#declare a few variables
num1 = 25
num2 = 100
num3 = 15

#define our method, we'll call it add_these_up. Our argument names will be x and y.

def add_these_up(x, y):
     sum = x + y
     return sum

# to use the function, we need to call it and pass some variables. We can even save the result in another variable!

new_number = add_these_up(num1, num2)
another_new_number = add_these_up(num1, num3)

# new_number now has a value of 125, and another_new_number has a value of 40

In this example, we defined a function that will add two numbers. We then called it twice, and placed the result in two new variables. We can define functions anywhere in our code, and then use them later. It doesn't matter if we have variables, or other functions, defined before it.

Hope this helps.