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Python None Keyword
The "None" keyword in Python is used when we need to declare a variable with no value at all. The interesting thing about the None keyword is that it is a constant value with no value at all.
"None" is neither a 0 nor an empty string like "". That is, "None" is none, nothing else. For example:
a = None b = 0 c = "" print(type(a)) print(type(b)) print(type(c))
The output is:
<class 'NoneType'> <class 'int'> <class 'str'>
It means that, like 0 is of the "int" type, "" is of the "str" type. Similarly, "None" is of the "NoneType" value.
Note: Python is a case-sensitive language; therefore, keep the first letter of the None keyword in capital letters, and the remaining 3 letters must be in small letters.
Python None Keyword Example
Here is an example of the None keyword in Python. This program demonstrates that a function with no return value will return None.
def funOne(): x = 10 def funTwo(): x = 100 return x x = funOne() print(x) x = funTwo() print(x)
The output is:
None 100
Advantages of the None keyword in Python
Following is a list of some of the advantages of the "None" keyword in Python.
- "None" can be used as a function's default argument value to show that the user didn't give any arguments.
- When defining a variable that will be given a value later, "none" can be used as a placeholder value.
- Before a value is given to a variable, it can be set to "none" to get it ready.
- "None" can be used to show that an iterator in a loop has reached its end.
Disadvantages of the None keyword in Python
Following is a list of some of the disadvantages of the "None" keyword in Python.
- "None" is a special value, so it can't be used everywhere where a value is needed. For instance, it can't be used as a dictionary key because dictionary keys have to be unchangeable and "None" isn't.
- Using "None" as the default value for an argument in a function can lead to unexpected results if the argument is mutable and the function changes it. In these situations, it's best to use a different default value, like an empty list or dictionary.
- If "None" is a valid value in the iterable being looped over, using "None" as a sentinel value can cause confusion and errors. It's best to use a sentinel value that is unique and can't be found in the iterable.
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