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Null Object In Python Example | Python Null Value Tutorial

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Null Object In Python Example | Python Null Value Tutorial is today’s topic. In Python, a ‘null‘ object is the singleton None. There’s no null value in Python; instead, there’s None.

As stated already, the most accurate way to test that something has been given None as the value is to use the is identity operator, which tests that two variables refer to the same object.

In other programming languages, for example, this is how you may create a null variable in PHP and Java.

#In Java

myVariable = null;

#In PHP

$myVariable = NULL;

If you need to evaluate a variable in the if condition, you may check this as follows in Java:

if(myVariable == null) {
  System.out.println(”Some output”);
}

How to use the ‘None’ in Python. I will use it in the if statement and a few compound data types.

How to test a variable is null in Python

As stated already, the most accurate way to test the something has been given None as the value is to use the is identity operator, which tests that two variables refer to the same object.

In Python, to represent an absence of the value, you can use a None value (types.NoneType.None) for objects and “” (or len() == 0) for strings.

Regarding the difference between “==” and “is” testing for object identity using “==” should be sufficient.

However, since the operation “is” is defined as an object identity operation, it is probably more correct to use it, rather than “==”. Not sure if there is even the speed difference.

#Python is Operator

See the following code.

# app.py

eleven = None
print(eleven is None)

See the following output.

➜  pyt python3 app.py
True
➜  pyt

#Check Using if…else condition

We can write the following code if we want to check if the value is None.

# app.py

value = None

if value is None:
    print('The value is null')
else:
    print('The value is not null')

In the above example, we have defined the variable called value and assign the None value.

Then, we have used the if…else condition to check the None value and if it does then return print statement with “The value is null.”

We can use the following code if we want to check if the name exists.

try:
    val
except NameError:
    pass  # val does not exist at all

#There is only be one None

The None is the built-in constant, as soon as you start Python, whether in module, class, or function. The NonType, by contrast, is not, you’d need to get a reference to it first by querying None for its class.

>>> NoneType
NameError: name 'NoneType' is not defined
>>> type(None)
NoneType

None cannot be overwritten.

Before Python 2.4, it was possible to reassign None, but not anymore. Not even as the class attribute or in the confines of a function.

#Testing if a value is None

Why do this

value is None

rather than

value==None

The first is equivalent to:

id(value)==id(None)

Whereas the expression value==None is applied like this

value.__eq(None)__

if the value is None, then you’ll get what you expected.

>>> nothing = function_that_does_nothing()
>>> nothing.__eq__(None)
True

The None has a distinctive status in Python language. It’s a preferred baseline value because many algorithms treat it as an exceptional value.

In such scenarios, it can be used as the flag to signal that the condition requires some special handling such as the setting of the default value.

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