Python Variables: Storing and Manipulating Data

Python Variables: Storing and Manipulating Data

In programming, a variable is a storage location that holds a value. Variables are an essential part of any programming language, as they allow you to store and manipulate data.

In Python, variables are created and assigned values using the = operator. For example:

message = "Hello, World!"

This creates a variable called message and assigns it the value "Hello, World!".

Variable Types

In Python, variables do not have a fixed type – you can assign any value to a variable, and the type of the value will be automatically determined. For example:

x = 10

y = "Hello"

In this code, x is an integer and y is a string. You can verify the type of a variable using the type() function:

print(type(x)) # Output: <class 'int'>

print(type(y)) # Output: <class 'str'>

It is important to note that in Python, strings are immutable – once you create a string, you cannot change it. For example:

name = "Alice"

name[0] = "B" 

 # This will raise a TypeError

If you need to modify a string, you must create a new string using string concatenation or string formatting. For example:

name = "Alice"

new_name = "B" + name[1:] 

# This creates a new string "Bice"

greeting = "Hello, {}!".format(name) 

 # This creates a new string "Hello, Alice!"

Variable Naming

In Python, variable names can contain letters, numbers, and underscores. However, they must start with a letter or an underscore. Variable names are case-sensitive, so name and Name are different variables.

It is good practice to use descriptive, meaningful names for your variables. For example, instead of using x and y, you might use first_name and last_name.

There are a few words that are reserved by Python and cannot be used as variable names. These words are called keywords, and they include True, False, None, and, or, not, if, else, for, while, def, class, try, except, finally, raise, import, from, as, return, global, nonlocal, and lambda.

Variable Scope

In Python, variables can be either global or local. A global variable is a variable that is defined outside of a function and can be accessed from anywhere in the program. A local variable is a variable that is defined inside a function and is only available within that function.

For example:

x = 10

# This is a global variable

def foo():

    y = 20 

# This is a local variable

print(y) 

# This will raise a NameError