How to Change the Value of a Variable in Python?

Are you wondering how to change the value of a variable in Python? Let me tell you everything about it. In this tutorial, I will show you different methods to change the value of a variable in Python with examples and complete code.

To change the value of a variable in Python using the direct assignment method, simply use the = operator to reassign a new value to the existing variable. For example, if you initially set x = 5 and later want to change it, you can do so by writing x = 10.

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Change the Value of a Variable in Python

Before changing the value of a Python variable, let us understand what a variable is.

A variable in Python is a symbolic name that refers to a value. Variables are created by assigning a value to a name using the = operator. For example:

x = 5

In this example, x is a variable that holds the value 5.

Now, let me show you different methods to change the value of a variable in Python with examples.

1. Direct Assignment

The simplest way to change the value of a variable is through direct assignment in Python. You can reassign a new value to an existing variable using the = operator. Here is an example.

x = 5
print(x)  # Output: 5

x = 10
print(x)  # Output: 10

In this example, the value of x is initially set to 5. Later, it is changed to 10 through direct assignment.

I executed the above Python code, and you can see the output in the screenshot below:

Change the Value of a Variable in Python

Check Declare a Variable Without Assigning a Value in Python

2. Using Arithmetic Operations

You can also change the value of a variable in Python by performing arithmetic operations and reassigning the result to the same variable.

Here is a simple example.

x = 5
print(x)  # Output: 5

x = x + 3
print(x)  # Output: 8

x -= 2
print(x)  # Output: 6

Here, the value of x is modified using the + and - operators. The shorthand operator -= is used to subtract 2 from x.

3. Using Functions

Variables in Python can be changed within functions. To modify a Python global variable inside a function, you need to use the global keyword.

x = 5

def change_value():
    global x
    x = 10

change_value()
print(x)  # Output: 10

In this example, the global keyword allows the function change_value to modify the global variable x.

Here is the output in the screenshot below:

How to Change the Value of a Variable in Python

Check out Access a Local Variable Outside a Function in Python Without Using global

4. Using Lists and Dictionaries

If you have a list or dictionary, you can change the value of elements within these data structures. Here are a few examples.

Lists

fruits = ['apple', 'banana', 'cherry']
print(fruits)  # Output: ['apple', 'banana', 'cherry']

fruits[1] = 'blueberry'
print(fruits)  # Output: ['apple', 'blueberry', 'cherry']

Dictionaries

person = {'name': 'John', 'age': 30}
print(person)  # Output: {'name': 'John', 'age': 30}

person['age'] = 31
print(person)  # Output: {'name': 'John', 'age': 31}

In these examples, we modify elements within a list and a dictionary.

5. Using Environment Variables

In some cases, you might want to change the value of environment variables in your Python script. This can be done using the os module. Here is a simple example.

import os

os.environ['MY_VAR'] = 'initial_value'
print(os.environ['MY_VAR'])  # Output: initial_value

os.environ['MY_VAR'] = 'new_value'
print(os.environ['MY_VAR'])  # Output: new_value

6. Using Classes and Objects

In object-oriented programming, you can change the value of instance variables within a class.

Here is how you can change the value of a variable in Python.

class Car:
    def __init__(self, make, model):
        self.make = make
        self.model = model

my_car = Car('Ford', 'Mustang')
print(my_car.model)  # Output: Mustang

my_car.model = 'F-150'
print(my_car.model)  # Output: F-150

In this example, we change the value of the model attribute of the my_car object.

Check out How to Use Global Variables in Python Classes?

Change the Value of a Variable in Python Example: Updating a Price List

Now, let me show you a real example of how to change the value of a variable in Python.

Suppose you want to update a price list for a grocery store.

prices = {
    'apple': 1.5,
    'banana': 0.75,
    'milk': 3.0
}

print(prices)  # Output: {'apple': 1.5, 'banana': 0.75, 'milk': 3.0}

# Updating the price of milk
prices['milk'] = 3.25
print(prices)  # Output: {'apple': 1.5, 'banana': 0.75, 'milk': 3.25}

# Adding a new item
prices['bread'] = 2.5
print(prices)  # Output: {'apple': 1.5, 'banana': 0.75, 'milk': 3.25, 'bread': 2.5}

In this example, we update the price of milk and add a new item, bread, to the price list. Here is the output in the screenshot below:

Change the Value of a Variable in Python Example

Conclusion

In this tutorial, I have explained how to change the value of a variable in Python with examples using different methods. I hope the real example also helps you learn how to change the value of a variable in Python.