What is Variable in Python: A Comprehensive Guide to Efficient Coding

Updated on July 26, 2024

Article Outline

A variable is basic to Python. It works as a storage block where data can be stored, along with its name. Variables may be viewed as entities that have the capacity to store various types of data that our programs can subsequently process. Understanding what is variable in Python and how to use it efficiently enables one to handle data comprehensively. For instance, instead of typing the same value every time it is needed, we just represent it once and then type the representation every time it needs typing.

 

Also, Python does not need us to declare the kind of variable we wish to use, unlike the majority of other languages. We only enter a value, and Python does the rest for us. This is not only time-saving but also makes our code neat and clean, hence easy to debug and modify. The said simplicity makes Python one of the most suitable languages for programming, whether for first-timers or professional developers.

Creating and Assigning Values to Variables

Creating a variable in Python is pretty easy. It is just a convenient way to select a name, make it stand for something, and then use the equals sign to make the assignment. This procedure is referred to as variable assignment.

Example:

name = input("Enter your name: ") age = int(input("Enter your age: ")) print(f"Hello, {name}! You are {age} years old.")

Output:

output

In this example, name and age are variables through which results can be obtained. The code illustrates how one can assign values to variables and then use these variables in further code execution.

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Data Types Associated with Python Variables

Here are the primary data types:

  • Integer (int): Whole numbers without a decimal point.
  • Float (float): Numbers with a decimal point.
  • String (str): A sequence of characters.
  • Boolean (bool): Represents True or False.
  • List (list): An ordered collection of items.
  • Tuple (tuple): An immutable ordered collection of items.
  • Dictionary (dict): A collection of key-value pairs.
  • Set (set): An unordered collection of unique items.

Rules and Best Practices for Naming Variables in Python

Naming variables appropriately is crucial for code readability and maintenance. Python has some rules and best practices for naming variables:

  • Variable names must begin with a letter or an underscore.
  • Variable names should contain only letters (a-z, A-Z), digits (0-9), and underscores.
  • Python variable names are case-sensitive. This means that the names “age” and “Age” are treated differently.
  • Keywords like False, True, None, and, or, not, etc., cannot be used as variable names.

Examples of valid variable names:

  • my_variable = 10
  • _variable = “underscore”
  • var123 = 5.67

Examples of invalid variable names:

  • 1st_variable = 10 (Cannot start with a digit)
  • my-variable = 20 (Hyphens are not allowed)
  • class = “Python” (‘class’ is a reserved keyword)

Reassigning Variables in Python

Variables defined in Python can be reassigned, which basically means that one can modify the value or type of a variable once it has been created.

Example:

value = 10 print(value) (Output: 10) value = "Python" print(value) (Output: Python) value = 3.14 print(value) (Output: 3.14)

Code Example with User Input

value = input("Enter any value: ") print(f"Initial value: {value} (type: {type(value)})") value = int(input("Enter an integer: ")) print(f"Updated value: {value} (type: {type(value)})") value = float(input("Enter a float: ")) print(f"Final value: {value} (type: {type(value)})")

Output:

output

Performing Multiple Assignments in Python

Multiple assignment in Python is one way to assign various values to variables in a single step. This feature is useful for assigning values for more than one variable in one line. This ability of Python helps create more organized and easy-to-read codes.

For instance, instead of writing:

  • a = 1
  • b = 2
  • c = 3

we can do this in one line:

  • a, b, c = 1, 2, 3

This is not only shorter but also cleaner.

Example with User Input

a, b, c = input("Enter three values separated by space: ").split() print(f"a = {a}, b = {b}, c = {c}")

Output:

output

Global vs. Local Variables in Python

We can divide the variables in Python into two sections namely Global Variables and Local Variables. Let’s understand both with suitable examples.

Global Variables

Global variables are declared outside a function and are accessible at all levels of the program.

Example:

x = "global" def my_function(): print(f"Inside function: {x}") my_function() print(f"Outside function: {x}")

Output:

output

Local Variables

Local variables are created inside a function and cannot be accessed in any other part of a program.

Example:

def my_function(): y = "local" print(f"Inside function: {y}") my_function() # print(f"Outside function: {y}")  # This will raise an error

Output:

output

If we try to access y outside the function, we’ll get an error because y is a local variable.

Example with User Input

Let’s create a function that uses both global and local variables, incorporating user input.

z = "global" def my_function(): z = input("Enter a local value: ") print(f"Inside function: {z}") my_function() print(f"Outside function: {z}")

Output:

output6

This example shows the difference in behavior between global and local variables, highlighting their scopes.

Modifying Global Variables Using the Global Keyword

Sometimes, we need to modify a global variable inside a function. For this, we use the global keyword. It allows us to update the global variable from within the function.

Example:

x = 5 def modify_global(): global x x = int(input("Enter a new value for the global variable: ")) print(f"Inside function, updated global x: {x}") modify_global() print(f"Outside function, updated global x: {x}")

Output:

output

In this example, we see how the global keyword allows us to modify the global variable x within the function.

Understanding Memory Management and Object References

Python comes with memory management capabilities built in. This basically implies that when we declare a variable, the Python interpreter reserves a place in the computer’s memory for that variable.

In Python, a variable is an object that has a reference to another object in memory. This implies that when we assign one variable to another, they will both point to the same object.

Example Code

a = input("Enter a list of numbers separated by space: ").split() b = a print(f"a: {a}, b: {b}") a.append(input("Enter a number to append to the list: ")) print(f"After appending: a: {a}, b: {b}")

Output:

output8

Arithmetic Operations with Python Variables

Arithmetic operations are basic operations in every programming language, including Python.

Addition

a = int(input("Enter the first number: ")) b = int(input("Enter the second number: ")) result = a + b print(f"Sum: {result}")

Output:

output9

Subtraction

a = int(input("Enter the first number: ")) b = int(input("Enter the second number: ")) result = a - b print(f"Difference: {result}")

Output:

output 10

Multiplication

a = int(input("Enter the first number: ")) b = int(input("Enter the second number: ")) result = a * b print(f"Product: {result}")

Output:

output11

Division

a = int(input("Enter the numerator: ")) b = int(input("Enter the denominator: ")) result = a / b print(f"Quotient: {result}")

Output:

output12

String Operations with Python Variables

In Python, strings are unique and can be handled in various forms. They are employed to manage text that may be words, sentences, or even paragraphs.

Concatenation

Combining two or more strings is called concatenation. We can do this using the + operator.

Example:

first_name = input("Enter your first name: ") last_name = input("Enter your last name: ") full_name = first_name + " " + last_name print(f"Full Name: {full_name}")

Output:

output13

Slicing

Slicing allows us to extract a portion of a string. We specify the start and end indices.

Example:

text = "Hello, World!" print(text[0:5])  # Output: Hello print(text[7:12])  # Output: World

Output:

output14

Formatting

String formatting is useful for inserting variables into strings. We use f-strings for this purpose.

Example:

name = input("Enter your name: ") age = int(input("Enter your age: ")) print(f"{name} is {age} years old.")

Output:

output15

Immutability

We cannot change a string in Python after creation; this is called immutability. Instead, we can create new strings.

Example:

original = "Hello" modified = original.replace("H", "J") print(f"Original: {original}, Modified: {modified}")

Output:

output16

Deleting Variables in Python

Sometimes, we need to delete variables to free up memory or remove them from the scope. We use the del statement for this purpose. Deleting variables helps in managing memory, especially when dealing with large datasets or temporary data.

Example:

variable = "Temporary data" print(variable)  # Output: Temporary data del variable # print(variable)  # This will raise a NameError because variable is deleted

Output:

output17

Conclusion

In this blog, we explored the world of Python variables. We learned what variables are in Python, how to declare and define variables with values, learned about value types and best practices in choosing the names of variables. Next, we learnt about changing the reference of variables, doing multiple assignments, and the differentiation between global and local variables. We also understood the string operations and memory management using the deletes statement. Understanding these key concepts enhances the coding ability and efficiency of any coder who is using Python language.

FAQs
We use the del statement to delete a variable.
You'll get a NameError. The reason behind this is that Python doesn’t know what you’re referring to.
Yes, Python allows us to assign multiple values to multiple variables in one line.

Updated on July 26, 2024

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