#100DaysOfCode in Python Transcripts
Chapter: Days 22-24: Decorators
Lecture: Function argument types: args and kwargs
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Alright, one thing we saw in the decorator
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was the args and keyword args being passed in
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and if you're new to python you might not be 100% aware
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of all the different options you have to call a function.
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So there's this great guide,
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The Hitchhiker's Guide to Python
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and it explains very well that you have positional,
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keyword, and two arbitrary kind of arguments,
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one is a list called *args and the other is a
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keyword argument dictionary, which is **kwargs
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and I just wanted to show a quick example
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how this all works, so let's define a get profile function
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and the only thing it's going to do is to
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bounce the different kind of arguments
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first let me just call it without anything
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and it should error because name is a positional argument
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which is required.
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You see that doesn't work
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and the error is pretty self explanatory
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so let me then call it with a positional argument
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and that worked, so the second type is keyword argument
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which is not required and at set here to the default value
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you can also set it to False, of course
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saying active equals False, and that works
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and then lets look at those two arbitrary kind of arguments
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which is list and dictionary, so first
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lets first do the arbitrary argument list
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so that allows me to, for example, here we do sports
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define one or more sports.
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And I really like basketball.
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Oops, yeah this is kind of strange that,
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well it says positional argument follows keyword argument
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so if you want to do it this way
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you have make sure this not to be a keyword argument
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so now it works. The reason is that the fourth
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type of arguments is an arbitrary keyword dictionary
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which goes towards the end. So let's pass in some words,
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and they go last, right? So we here have the dictionary
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of Pythonista and Topcoder, and that was the reason
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we got the error before because the keyword arguments
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always should go last, and to show arguments in action
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I define this show args decorator that prints the args
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before calling the function and prints the keyword arguments
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after calling the function,
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so just to put it into the context of the decorators
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we are dealing with here. So we have show args
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and I'm going to redefine the function, and this time
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not to confuse it with the behavior of the decorator
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I'm just going to print something else.
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Hi from
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the get profile
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function
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okay now lets see what happens
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if I call and get profile again, now that it is decorated
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of course I need to run the cell.
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And here you see, so in the decorator it first
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brings the args, then it does the actual function work
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which is printing 'hi' from the get profile function
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and then we're at the after stage of the decorator
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printing the keyword arguments.
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So here we see that the *args contains
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the position arguments, keyword arguments, and the arbitrary
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argument list, and the **kwargs contains then
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the arbitrary keyword argument dictionary, so here you see
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all those arguments actually being passed into the decorator
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and hopefully now you have a better understanding what
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*args and **kwargs means
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and the different kind of ways
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we can call function in python
