Global Keyword in Python
In Python, variables that are defined inside a function are considered to be local to that function. However, there may be situations where you want to modify a variable that is defined outside of a function, inside that function. This is where the global keyword comes in.
The global keyword is used to indicate that a variable is a global variable, which means that it is defined outside of any function and can be accessed from any part of the program. When you use the global keyword inside a function, you are telling Python that you want to modify the value of a global variable, rather than creating a new local variable with the same name.
Here's an example:
x = 10
def add_to_x(num):
global x
x += num
add_to_x(5)
print(x)
Output:
15
In this example, x is a global variable that is defined outside of the function add_to_x(). The global keyword is used inside the function to indicate that we want to modify the global variable x, rather than creating a new local variable with the same name. When we call the add_to_x() function and pass in the argument 5, the value of x is updated to 15.
Without the global keyword, Python would assume that x is a local variable that is defined inside the function, and would create a new local variable with the same name instead of modifying the global variable. Here's an example:
x = 10
def add_to_x(num):
x += num
add_to_x(5)
print(x)
Output:
UnboundLocalError: local variable 'x' referenced before assignment
In this example, we did not use the global keyword inside the function, so Python assumed that x is a local variable that is defined inside the function. When we try to modify the value of x inside the function, we get an error message because x has not been assigned a value yet.
Conclusion
The global keyword is a powerful tool that allows you to modify global variables from within functions. When you use the global keyword, you are telling Python that you want to modify the value of a global variable, rather than creating a new local variable with the same name. Understanding how to use the global keyword is an important part of writing efficient and effective Python code. However, it's important to use the global keyword with caution, as it can make your code more difficult to read and understand.
Happy Learning!! Happy Coding!!
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