What is the difference between a module-level variable and a global variable in Python?
Davide S

In Python, there are module-level variables and global variables, which have different scopes and behaviors within a program. Here's a detailed explanation of the differences between module-level variables and global variables: Module-Level Variables: - Scope: Module-level variables are defined at the top level of a module file and are accessible within that module only. They have module-level scope, which means they can be accessed from any function or class within the module. - Declaration: Module-level variables are typically defined outside of any function or class, at the top level of the module file. They are accessible throughout the module. - Behavior: Module-level variables maintain their value throughout the execution of the program. They can be accessed and modified from any part of the module. If multiple modules import the same module, they will share the same instance of the module-level variable. - Example:

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# module.py
module_variable = 10

def function1():
    print(module_variable)

def function2():
    module_variable = 20
    print(module_variable)

# main.py
import module

module.function1()  # Output: 10
module.function2()  # Output: 20

In this example,module_variable is a module-level variable defined in themodule.py file. It can be accessed and modified within the module's functions. Whenfunction1() is called, it prints the value ofmodule_variable as 10. Infunction2(), a new local variable with the same name is created and assigned a value of 20, which shadows the module-level variable. Global Variables: - Scope: Global variables are defined outside of any function or class and can be accessed throughout the entire program. They have global scope and can be accessed from any module or function within the program. - Declaration: Global variables are typically defined at the top level of the program or within a module, outside of any function or class. They are accessible from any part of the program. - Behavior: Global variables maintain their value throughout the entire program's execution. They can be accessed and modified from any module or function within the program, provided they are declared as global within the respective function or module. - Example:

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global_variable = 10

def function1():
    print(global_variable)

def function2():
    global global_variable
    global_variable = 20
    print(global_variable)

function1()  # Output: 10
function2()  # Output: 20

In this example,global_variable is a global variable defined at the top level of the program. It can be accessed and modified within any function or module. Infunction1(), it prints the value ofglobal_variable as 10. Infunction2(), theglobal keyword is used to indicate that the variable being modified is the global variable. The assignmentglobal_variable = 20 modifies the global variable, and subsequent calls tofunction1() will print the updated value of 20. Summary: In summary, module-level variables and global variables differ in terms of their scope and accessibility within a program. Module-level variables are defined at the top level of a module and are accessible within that module only, while global variables are defined outside of any function or class and can be accessed throughout the entire program. Module-level variables are limited to the module they are defined in, while global variables are accessible from any module or function within the program. Understanding the differences between module-level variables and global variables helps you manage and control the scope of your variables effectively within your Python programs. It's important to consider the specific requirements and context of your program when deciding which type of variable to use.

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