Python why none

So, there is no way we can alter the attributes of None. We cannot create other instances of NoneType. None is not the same as False. None cannot have new attributes. Existing attributes of None cannot be changed. None is not an empty string. None is not 0. If the function doesn't return anything that means its None in Python. We cannot even change the reference to None by assigning values to it. Comparing None to anything will always return False except None itself.

Let us understand the need of NONE with example. Consider a login form, with the backend language as Python to connect to a database. If we wish to check whether we have formed a connection to the specified database, we can assign NONE to the database connection object and verify if the connection is secured or not.

Moreover, by assigning a variable to NONE, it depicts that no-value or a null value is represented by the specific variable. Final: Finally I've got my answer from looking to different answers. Improve this question. Peter Mortensen 29k 21 21 gold badges 97 97 silver badges bronze badges. That book isn't too helpful; None is not a default empty state for variables. Off the top of my head php is the only language whose null value is equivalent to the default empty state for a variable.

Now I'm wondering what other languages do that. Right, which is different from null , a point I'm failing to make to MartijnPieters in his answer. Show 3 more comments. Active Oldest Votes. Since Python programmers as a rule would never say Assigning a value of None to a variable is one way to reset it to its original, empty state.

One analogy which may help: In Python, variable names are like stickers put on objects. Improve this answer. Where can i find more info about Python's built-in names? This is a great explanation for a non-programmer. Thank you very much! Add a comment. There is only one copy of that object in a given Python interpreter session. Community Bot 1 1 1 silver badge. I think the semantics of emptiness are different from those of undefinedness. JavaScript has both undefined and null. It is a signal object, with much the same meaning.

MartijnPieters: SQL is a programming language, just a very specific purpose, declarative one. See stackoverflow. This is what the Python documentation has got to say about None : The sole value of types. Changed in version 2. Let's confirm the type of None first print type None print None. Let's try that print types. IntType print types. Let's check how we have implemented None internally. Let's try and add new attributes to None setattr types. NoneType, 'somefield', 'somevalue' setattr None, 'somefield', 'somevalue' None.

We cannot create other instances of NoneType We cannot even change the reference to None by assigning values to it.

Happy knowing None :. Very very interesting!! Jadav Bheda Jadav Bheda 4, 1 1 gold badge 25 25 silver badges 26 26 bronze badges. GrvTyagi GrvTyagi 3, 31 31 silver badges 35 35 bronze badges.

Dab Brill Dab Brill 51 4 4 bronze badges. None evaluates to False. Azeirah Azeirah 5, 6 6 gold badges 20 20 silver badges 40 40 bronze badges. It does not , as you suggest, print nothing. IDLE, like the Python interactive interpreter prompt, explicitly hides None if that is the result of an expression, mostly to not clutter up the output. Rohan Khude 3, 5 5 gold badges 46 46 silver badges 39 39 bronze badges. Sree Latha Sree Latha 1. Sign up or log in Sign up using Google.

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