The Unhealthy Behavior Called Anorexia Video
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Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Anyone tinkering with Python long enough has been bitten or torn to pieces by the following issue:. Python novices would expect this function to always return a list with only one element: [5]. The result is instead very check this out, and very astonishing for a novice :. A manager of mine once had his first encounter with this feature, and called it "a dramatic design flaw" of the language. I replied that the behavior had an underlying explanation, and it is indeed very puzzling and unexpected if you don't The Unhealthy Behavior Called Anorexia the Behavvior.
However, I was not able to answer to myself the following question: what is the reason for binding the default argument The Unhealthy Behavior Called Anorexia function definition, and not at function execution?
I doubt the experienced behavior has a practical use who really used static variables in C, without breeding bugs? Behaviior made an interesting example. Together with most of your comments and Utaal's in particular, I elaborated further:.
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To me, it seems that the design decision was relative to where to put the scope of parameters: inside the function or "together" with it? Doing the binding inside the function would mean that x is effectively bound to the specified default when the function is called, not defined, something that would present a deep flaw: the def line would be "hybrid" in the sense that part of the binding of the function object would happen at definition, and part assignment of default parameters at function invocation time. The actual behavior is more consistent: everything of that line gets evaluated when that line is executed, meaning at function definition. Actually, this is not a design The Unhealthy Behavior Called Anorexia, and it is not because of internals, or performance.
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It comes simply from the fact that functions in Python are first-class objects, and not only a piece of code. As soon as you get to think into this way, then it completely makes sense: a function is an object Tne evaluated on its definition; default parameters are kind of "member data" and therefore their state may change from one call to the other - exactly as in The Unhealthy Behavior Called Anorexia other object.
In any case, Effbot has a very Tje explanation of the reasons for this behavior in Default Parameter Values in Python. I found it very clear, and I really suggest reading it for a better knowledge of how function objects work. When I see the declaration of eat, the least astonishing thing is to think that if the first parameter is not given, that it will be equal to the tuple "apples", "bananas", "loganberries". This would be https://amazonia.fiocruz.br/scdp/essay/essay-writing-format-cbse-class-12/kate-chopin-feminism-and-feminism.php astonishing IMO than discovering that your foo function above was mutating the list. The real problem lies with mutable variables, and all languages have this problem to some extent. Here's a question: suppose in Java I have the The Unhealthy Behavior Called Anorexia code:.
Now, does my map use the value of the StringBuffer key when it was placed into the map, or does it store the key by reference?]
Let's try be reasonable.