Python global keyword is used to specify that a given variable refers to a variable defined in the global scope.
It is used to explicitly indicate that a variable inside a function should refer to the global variable with the same name.
In Python, a variable defined within a function is considered local to that function by default. It exists only within the scope of the function and cannot be accessed or modified outside of it.
However, sometimes it becomes necessary to access or modify a variable that resides in the global scope, from within a function.
This is where the global keyword comes into play.
It allows you to modify the value of a global variable from within a local scope, such as a function or method.
Syntax
To use the global keyword, you simply need to include it before the variable name inside a function or method where you intend to modify its value.
Here’s the general syntax:
def my_function():
global global_variable
# Function body
By prefixing the variable name with global, you inform Python that any reference to that variable within the function should refer to the global variable rather than creating a new local variable.
Let’s look at a simple example to illustrate the usage of the global keyword:
count = 0
def increment():
global count
count += 1
print(count) # Output: 0
increment()
print(count) # Output: 1
In the example above, we have a global variable count initialized to 0.
The increment() function uses the global keyword to access and modify the global variable.
After calling the increment() function, the value of count is incremented by 1, as reflected in the output.
Conclusion
The global keyword in Python allows you to access and modify global variables from within local scopes, such as functions or methods.
While it can be a useful tool, it’s important to use it judiciously and be mindful of potential pitfalls.