To check if a variable is Null
in Python, there are some methods we have effectively tested: the is
operator, Use try/except
and the non-equal operator. Follow the article to better understand.
None and Null in Python
Nowaday, the keyword null
is used in many programming languages to represent that the pointer is not pointing to any value. NULL
is equivalent to 0. A newly created pointer points “miscellaneous” to a particular memory area. Assign the pointer to NULL
to make sure it points to 0. Even though 0 is an invalid location, it’s easier to manage than when the pointer points to an area we don’t know.
In Python, there is no null
but None
.
None
is a specific object indicating that the object is missing the presence of a value. The Python Null
object is the singleton None
.
In other words None
in Python is similar to the Null
keyword in other programming languages.
Check if a variable is Null in Python
Use the ‘is’ operator
The is
operator is used to compare the memory addresses of two arguments. Everything in Python is an object, and each object has its memory address. The is
operator checks if two variables refer to the same object in memory.
Example:
myVar = None # Check variable myVar is Null if myVar is None: print('The value of the variable myVar is None (null)')
Output:
The value of the variable myVar is None (null)
In the above example, I declared value = None
and then used the is
operator to check if value
has None
or not. If value
is valid, then execute the if
statement; otherwise execute the else
statement.
Note:
Do not use the ==
operator to check for the value None
. Because in some cases will lead to erroneous results.
Use try/except
Use try/except
block to check if the variable is None
.
Example:
The ‘if’ statement in ‘try’ to check variable ‘value’ exists and the value of ‘value’ is ‘none’
try: if myVar is None: print('The value of the variable myVar is None (null)') # Check name exists except NameError: print("The variable myVar does not exist")
Output:
The variable myVar does not exist
Use the non-equal operator
Another method to check if a variable is None
is using the non-equal or !=
operator.
Example:
myVar = 1 if myVar != None: print('The variable is not null')
Output:
The variable is not null
Summary
Here are ways to help you check if a variable is Null
in Python. Or, if you have any questions about this topic, leave a comment below. I will answer your questions.
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My name is Jason Wilson, you can call me Jason. My major is information technology, and I am proficient in C++, Python, and Java. I hope my writings are useful to you while you study programming languages.
Name of the university: HHAU
Major: IT
Programming Languages: C++, Python, Java