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What is None, and how to check a None variable in Python? You might have heard about the term Null if you are familiar with various programming languages such as C or Java. Simply, Null is just as zero in those programming languages. However, in Python, Null is different. Scrolling down to know everything about checking None in Python!
1. What is None in Python?
In Python, None is a NoneType class, which is used for defining null variables or objects. In fact, None is considered the only instance in the NoneType class. You can not instantiate the None objects because the results will return in the same one. In another word, None is seen as a singleton.
In the field of programming, many programmers prefer using None because it is evaluated as a special value which is significantly useful for most algorithm treatments. None is widely used for representing other value absences in various places of programming language and standard library.
2. Interesting Facts About None in Python
Most beginners tend to misunderstand None and confuse None for Null. Below are some facts that would help you to easier acquire more about the None object.
- None is different from False.
- None is not zero.
- None is also not an empty string.
- You can not compare None to other variables because it will turn out False.
3. How to Check a None Variable in Python
There are different values that can be stored by a variable in Python, such as integer, float, character, and other types of values. However, in case you face a variable that does not belong to NoneType, you must know how to check whether that variable is None. Therefore, here we will provide you with 4 main ways to check None variables in Python as the following:
- Checking a None variable in Python by using the Keyword “is”
- Checking a None variable in Python by using the Function “isinstance ()”
- Checking a None variable in Python by using the Dictionary
- Checking a None variable in Python by using the Block “try” and “except.”
3.1 How to Check a None Variable in Python by Using the Keyword “is”
In Python, if you want to test a condition, you can apply the statement “if”. On the other hand, in case you want to check if there is any None variable, you can utilize the keyword “is”. The purpose of using this keyword is to check if two variables navigate to one object.
Example:
a = None
b = 5
if(a is None):
print("A is None")
if(b is not None):
print("B is not None")
Output:
A is None
B is not None
3.2 How to Check a None Variable in Python by Using the Function “isinstance”
To assess if an object is included in any variable type, you can use the function “instance ()”. For checking the None variables in Python, you can apply type(None). Then, a tuple will be returned. Its first element represents the variable that has the value you want to test. The remaining one is “True” or “False,” no matter whether that variable meets the needed type.
Example:
a = None
b = 5
print((a, isinstance(a, type(None))))
print((b, isinstance(b, type(None))))
Output:
(None, True)
(5, False)
3.3 How to Check a None Variable in Python by Using the Dictionary
A dictionary in Python is the storage of key-value pairs. You can use the Dictionary to access whether there is a None variable. Though this technique is unconventional, it offers the expected result.
Example:
a = None
dict = {None: 'The variable is None'}
print(dict[a])
Output:
The variable is None
3.4 How to Check a None Variable in Python by Using the Block “try” and “except”
In case the process of code treatments raises exceptions, the block “try…except” will be an ideal solution. As mentioned previously, when Python identifies that a None variable is operated, it might increase the exception of NoneType.
You can definitely handle your code with the variable suspected as None in the block of “try”. If the result clarifies that it is None, the exception will be caught by the catching block.
Example:
a = None
b = 5
try:
c = a + b
except:
print("Some variable is None")
Output:
Some variable is None
Through this article, you have been supported with knowledge and tutorials about how to check a None variable in Python. None is an optimal and powerful tool to identify empty values in Python. Hope that all shared information above will be a helping hand for use in working with NoneType. If you have further confusion, keep waiting on the upcoming article for more interesting IT solutions!
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