Lecture 127:-  Local & Global Variables

In programming, local and global variables refer to the scope or visibility of variables within different parts of your code. Let's delve into each of these concepts:

Local Variables: Local variables are variables that are declared and used within a specific block of code, such as a function, method, or a block within a function. These variables have a limited scope and are only accessible within the block in which they are defined.

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def my_function(): x = 10 # Local variable print(x) my_function() # print(x) would result in an error since x is a local variable and is not accessible here.

Local variables are useful for encapsulating data that is only relevant within a specific context, such as temporary calculations or intermediate results within a function.

Global Variables: Global variables are variables that are defined outside of any function or block. They have a global scope, which means they can be accessed from anywhere within the code, including within functions.

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y = 20 # Global variable def my_function(): print(y) # Accessing the global variable my_function() print(y) # Global variable can be accessed outside the function as well

While global variables provide easy access to data throughout the code, it's important to use them judiciously. Overusing global variables can lead to code that is harder to understand, test, and maintain, as changes made to global variables can have unintended consequences across the program.

Local vs. Global: When a local variable has the same name as a global variable, the local variable takes precedence within its scope. This is known as "variable shadowing."

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z = 30 # Global variable def another_function(): z = 40 # Local variable with the same name as the global variable print(z) # Prints the local variable another_function() print(z) # Prints the global variable

To modify a global variable within a function, you can use the global keyword to indicate that you're referring to the global variable, not creating a new local variable with the same name.

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count = 0 # Global variable def increment_counter(): global count count += 1 increment_counter() print(count) # Output: 1

In general, it's a good practice to use local variables whenever possible to encapsulate data within a specific context and reduce the potential for unintended side effects. Global variables should be used sparingly and with careful consideration.