Namespaces and Scope
Global vs Local Variables
Scope: The scope of a variable determines where in your code that variable is accessible.
- Global Variables: Declared outside of any function. Accessible from anywhere in the program after its declaration.
global_var = 10
def my_function():
print(global_var) # Accessing global variable inside a function
my_function() # Output: 10
print(global_var) # Output: 10
- Local Variables: Declared inside a function. Only accessible within that function.
def my_function():
local_var = 5
print(local_var) # Accessing local variable
my_function() # Output: 5
#print(local_var) # This will cause a NameError because local_var is not accessible here.
Modifying Global Variables within Functions:
To modify a global variable from within a function, you must use the global keyword:
global_var = 10
def modify_global():
global global_var # Declare that we are modifying the global variable
global_var = 20
modify_global()
print(global_var) # Output: 20
Without the global keyword, a new local variable with the same name would be created.
Potential Issues:
- Name clashes: Using the same name for global and local variables can lead to confusion and unexpected behavior. It’s generally good practice to avoid this.
- Readability: Overuse of global variables can make code harder to understand and maintain, as it becomes difficult to track where a variable’s value might be changed. Variable Naming Conventions It’s generally better to pass data as arguments and return values.
Related Notes: