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None python value




Why does it work like this, because None works for equivalence like null , and there is no value in a .

According to the idea, it should turn out to be True because the value None has nothing or is equal to 0 or False , but for some reason when entering such data into the variable a returns False Could you explain why this is happening.

& gt; & gt; & gt; a = ""
& gt; & gt; & gt; a == None
& gt; & gt; & gt; a = "0"
& gt; & gt; & gt; a == None
& gt; & gt; & gt; a = 0
& gt; & gt; & gt; a == None
& gt; & gt; & gt;

Answer 1, authority 100%

a you have this name. Using the = operator you attach this name to different objects (empty string '' , string with character '0' (U + 0030), integer number 0 – objects are created by the corresponding constants in the source code). Strings are objects of type str in Python. An integer is an int object.

a == None compares these objects to a None object. No object of type str or int can be equal to None. As an aside, None is also a Python object (of type NoneType). It exists in a single copy in the program, so it should be compared using the is operator: a is None (is the same object or not. Purpose == compare values ​​objects).

You were probably interested in the concept of “truthiness” in Python (meaning in a boolean context) and a really empty string (like other empty containers) and 0 integer are Falsey in Python:

if not a:
  print (f '{a! r} is Falsey')

See Truth Value Testing .

Note '0' is not an empty string, so bool ('0') is True . Python is a strongly typed language. String to a number or to None, the object will not implicitly turn into . The names themselves, such as a , can refer to any object at different times. But the name must refer to some object, otherwise you will get NameError .

Answer 2, authority 100%

In the first case, the a variable contains an empty string. The second line contains a zero character. In the third, the number 0. In all three cases, there is something in the variable.

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