Variables in Python are locations inside the computer’s memory where we can store certain values that can be assigned by the user. So, when we declare a variable with some values the Python interpreter automatically detects its data type.

Every value in Python is characterized by different data types like Numbers, List, Tuple, Strings, Dictionary, etc.

Declaring a Variable in Python

Declaring variables in Python and printing them using the print() function can be a very easy task.

city = "Kolkata"
sum = 100
a = 6.10
print(city)
print(sum)
print(a)

The output of this will be:

Kolkata
100
6.10

Here, we can see that we created three variables city, sum & a.

Each one of them was of different data types, city was a string, sum was an integer & a was a float type of data.

Assigning Multiple Variables in Python

We can assign multiple variables with different values together in a single line in Python.

city,sum,a = "Kolkata",100,6.10
print(city)
print(sum)
print(a)

The output of this will be:

Kolkata
100
6.10

Here, we created three variables in Python in a single line of code. Then we used the print() function to print them out one by one.

Rules for Variables in Python

Python variables are written under a certain set of rules:

1. Variables can be a combination of lowercase and uppercase letters, numbers, or underscore( _ ).
2. Variables cannot start with a number.
3. We cannot use special characters like $, (, * %, etc in declaring a variable.
4. Variables in Python cannot be named using any Keywords.
5. Variables are case-sensitive.

Re-declaring Variables in Python

We can re-declare the value of a variable in Python.

Example Re-declaring Variables in Python

a = "Kolkata"
print(a)
a = 100
print(a)

The output of this will be:

Kolkata
100

Here, we can see that the variable a was string data type in the beginning, and then we changed it to an integer data type.

Local & Global Variables in Python

Two major types of variables in Python are the Local and the Global types.

Example of local and global variables in Python

x = 5
y = 10
def add(a,b)
    sum = a + b
    return sum
print(add(x,y))

The output of this will be:

15

Here, we declare two variables x & y in the beginning. These are known as global variables because we can use them anywhere in the Python program. We use a variable named sum inside the add function.

This variable cannot be used anywhere else outside the add function. So this makes it a local variable.

Deleting Variables in Python

We can delete a variable in Python using the del keyword.

Example how to delete a variable in Python using del keyword

a = 100
del a
print(a)

The output of this will be:

Traceback (most recent call last):
File "main.py", line 3, in
print(a)
NameError: name 'a' is not defined

Here, we declared an integer variable and then deleted it using the del keyword.

When we tried the print() function, it gave an error which proves that the variable is successfully deleted.

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