Declaring a variable without a value in Python
A variable is a reserved memory location that can store some value. In other words, variables in a Python program provide data to the computer to process operations. Every value in Python has a data type. There are numbers, lists, tuples, etc. in Python.
We will now discuss how to declare a variable in Python without assigning any value to it.
In Python, we use Nonethe keyword to declare a variable without a value.
Python is dynamic, so there is no need to declare variables, and they automatically exist in the first scope they are assigned to. All that is needed is a regular assignment statement.
NoneIs NoneTypea special object of type . It refers to the NULL value or some unavailable value. If we don't want to give it any value, we can assign the variable as None.
For example,
var = None
This is convenient, because you'll never end up with uninitialized variables. But it doesn't mean you won't end up with incorrectly initialized variables, so you should be careful.
Declaring a variable without a value in Python using variable annotation
For those using Python 3.6+, you can use variable annotations in this case.
Type annotations were introduced in PEP 484. Its main focus is on function annotations. However, it also introduced the concept of type annotations to annotate variables.
We can use this to determine the type of a variable instead of initializing it with any value.
The new PEP 526 introduces syntax for annotating variables (both class variables and instance variables) of required types without annotations.
For example,
from typing import get_type_hints
var: str
Thus, it declares a varvariable named with no such initial value.
Declare variables with no values in Python using empty strings or lists
Apart from the methods discussed above, we can also assign an empty string or a list to a variable.
Technically, we assign a value to the variable, but it is empty and updated according to our needs.
var = ""
lst = []
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