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Python Declare Variable Without Value

Posted on by Nrich Systems

Here’s a great article from The Crazy Programmer

We know that in many languages like C, C++, Java, when we want to use any variable then first we have to declare that variable and after that, we can use that variable in our program.

The languages listed above are high-level languages that are compiled before it runs, but Python is a dynamically compiled language. In python, we don’t have to specify which type of variable we are going to use. Simply we have to write the name of a variable and we can use it as per our own like we can store an integer value or a string value in the same variable.

So the question comes, is it possible to declare a variable without value in python?

The answer is no, we cannot declare a variable without value in python. I will demonstrate an example to prove my point.

Let us see a basic addition of 2 numbers program in Python.

num1 = int ( input ( " Enter Number 1 : " ) )
num2 = int ( input( " Enter Number 2 : " ) )

print ( f " Sum is { num1 + num2 } " )

Output:

PS C :  Users  ASUS  Desktop  TheCrazyProgrammer Work > python -u " c :  Users  ASUS  Desktop  TheCrazyProgrammer Work  test.py "
Enter Number 1 : 32
Enter Number 2 : 5
Sum is 37

Here, we are directly using the variable without declaring anything previously, because as python is a dynamic language it allows variables to be created at run time.

Now, we are going to see an example in which we will not assign any value to the variable in python, and let’s see the output in that case.

val

for i in range ( 10 ) :
    if ( val == None and i == 5 ) :
        print ( " I am in the if Block " )
    print ( i )

When we run this program then we will get an error.

Output:

PS C :  Users  ASUS  Desktop  TheCrazyProgrammer Work > python -u " c :  Users  ASUS  Desktop  TheCrazyProgrammer Work  test.py "
Traceback ( most recent call last ) :
  File " c :  Users  ASUS  Desktop  TheCrazyProgrammer Work  test.py " , line 47 , in < module >
    val
NameError : name ' val ' is not defined

We got NameError which tells us that the name of the variable we have used in our program is not defined.

We have not defined any value of that variable so the interpreter is not able to recognize the variable and it throws an error.

Python Declare Variable Without Value

We are going to see a trick to initialize any variable without a value, actually, this is not a trick but a way to initialize a variable when we do not want any value to set up at declaration time.

We can do it by setting the value of the variable to None.

We will modify our previous code to that it will be executed successfully.

val = None

for i in range ( 10 ) :
    if ( val == None and i == 5 ) : 
        print( " I am in the if Block " )
    print ( i )

Output:

PS C :  Users  ASUS  Desktop  TheCrazyProgrammer Work > python - u " c :  Users  ASUS  Desktop  TheCrazyProgrammer Work  test.py "
0
1
2
3
4
I am in the if Block
5
6
7
8
9

We can see that our program is executed successfully.

In python, we cannot declare a variable without any value because python is a dynamic language and it does not allow variable without value. In python it is not necessary to declare the datatype of the variable, we can directly use the variable in our programs.

The post Python Declare Variable Without Value appeared first on The Crazy Programmer.

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