Adventures in Machine Learning

Mastering Global Variables in Python: Deletion and Modification

Python is a versatile programming language that has gained popularity in recent years. Its flexibility and readability make it a popular choice for developers around the world.

In this article, we will discuss two fundamental aspects of Python programming: deleting global variables and changing the value of global variables inside a function.

Delete global variable from inside a function in Python

Deleting global variables is essential in situations where you no longer need the data assigned to the variable or want to free up memory space. In Python, the del statement is used to delete an object from memory.

However, deleting a global variable from a function is not as straightforward as it may seem. Since functions operate within their own scopes, it is not possible to delete a global variable from inside a function without explicitly marking it as global.

To mark a variable as global, you need to use the global keyword. This keyword informs Python that the variable is a global variable and it should be treated as such, even when accessed inside a function.

Here’s an example:

“`

x = 10

def delete_global_variable():

global x

del x

“`

In this example, we have defined a global variable `x` with a value of 10. We then define a function `delete_global_variable()` that deletes `x` using the del statement.

However, before the variable can be deleted, we need to mark it as global by using the `global` keyword. This ensures that the function knows that `x` is a global variable and not a locally defined variable.

Python: Change the value of a Global variable in a Function

Sometimes, you may need to change the value of a global variable inside a function. This can be useful in situations where you want to update the value of a global variable based on some computation or logic applied inside the function.

However, changing the value of a global variable inside a function requires careful attention to avoid unintended side effects. To change the value of a global variable inside a function, you need to follow a few steps.

First, you need to mark the variable as global using the `global` keyword. This tells Python that the variable is a global variable and not a locally defined variable.

If you don’t mark the variable as global, Python will assume that it is a local variable and will not modify its value outside the function. Secondly, you need to read the value of the global variable before changing it.

This is because if you don’t read the value of the global variable, Python will throw an `UnboundLocalError` error. This is because Python assumes that if you modify the global variable inside a function, it must be a local variable.

Here’s an example:

“`

x = 10

def

change_global_variable():

global x

print(“The value of x before changing is:”, x)

x = 20

print(“The value of x after changing is:”, x)

“`

In this example, we have defined a global variable `x` with a value of 10. We then define a function `

change_global_variable()` that changes the value of `x` to 20.

Before changing the value of `x`, we first print its current value using the `print()` statement. Since we have marked `x` as global, Python knows that it is not a local variable and will modify its value outside the function.

We then assign a new value of 20 to `x`. Finally, we print the value of `x` again to confirm the change.

Conclusion

Python is an expressive and versatile programming language that is widely used by developers worldwide. In this article, we discussed two important concepts in Python programming: deleting global variables and changing the value of global variables inside a function.

By following the steps outlined in this article, you can easily modify global variables without running into any errors or unintended side effects. In programming, global variables are variables that are defined outside of any function.

Global variables are accessible from any part of the program. They are useful for storing values that need to be shared between different functions and modules.

However, in some situations, you may want to delete a global variable or change its value from inside a function. Here we will discuss these topics in more detail.

Deleting Global Variables from Inside Functions

In Python, deleting a global variable from within a function requires you to use the `global` keyword to explicitly declare the variable as global. The `global` keyword tells the interpreter that the variable is a global variable, and therefore, it is accessible from any part of the program.

Consider the following example:

“`

x = “Hello, World”

def delete_variable():

global x

del x

delete_variable()

print(x)

“`

In this example, the `delete_variable` function uses the `global` keyword to tell Python that `x` is a global variable. The `del` statement removes the variable `x` from memory.

When we try to print `x` after running `delete_variable()`, Python raises an error because the variable `x` no longer exists. In summary, when you delete a global variable from a function, you must:

1.

Declare the variable as global using the `global` keyword. 2.

Use the `del` keyword to remove the variable from memory.

Changing the Value of Global Variables inside Functions

In Python, changing the value of a global variable inside a function also requires the use of the `global` keyword. When changing the value of a global variable inside a function, you must read the value of the variable, change it, and then assign the new value back to the variable.

Consider the following example:

“`

x = 10

def

change_global_variable():

global x

print(“The value of x before change is:”, x)

x = 20

print(“The value of x after change is:”, x)

change_global_variable()

print(“The value of x outside function is:”, x)

“`

In this example, the `change_global_variable` function changes the value of `x` from 10 to 20. The `global` keyword is used to modify the value of the global variable `x` from inside the function.

Before the value of `x` is changed, we print the current value of `x` using the `print()` function.

When we call `

change_global_variable()`, it modifies the global variable `x`.

We can, therefore, print the new value of `x` inside the function and outside the function. In summary, when you change the value of a global variable inside a function, you must:

1.

Declare the variable as global using the `global` keyword. 2.

Read the value of the global variable. 3.

Modify the value of the variable. 4.

Assign the new value back to the variable.

When to Use Global Variables

Global variables are useful when you want to store data that is needed throughout the program’s execution. However, overusing global variables can lead to code that is difficult to understand and maintain.

In general, it is best to limit the use of global variables and keep them to a minimum. Here are some guidelines on when to use global variables:

1.

Use global variables when the data needs to be accessed from multiple parts of the program. 2.

Use global variables when the data is used frequently. 3.

Use global variables when the data is constant. Here are some guidelines on when not to use global variables:

1.

Avoid global variables when the data is only used in one part of the program. 2.

Avoid global variables when the data needs to be modified frequently. 3.

Avoid global variables when the data is mutable.

Conclusion

In this article, we discussed the important concepts of deleting global variables and changing the value of global variables inside a function. We also discussed some guidelines on when to use global variables.

By following the steps outlined in this article, you can modify global variables without encountering any issues. However, it is essential to use global variables judiciously to avoid creating code that is difficult to maintain and understand.

In conclusion, the article explained the fundamental concepts of deleting global variables and changing the values of global variables inside a function in Python. To delete or modify global variables inside functions, we need to use the `global` keyword to explicitly declare the variable as a global variable.

Global variables are useful for storing data that needs to be accessed from different parts of the program, but overusing them can lead to code that is difficult to understand and maintain. By using global variables judiciously and following the steps outlined in this article, we can modify global variables without encountering any issues.

Overall, understanding how to delete and modify global variables is essential to writing effective and efficient Python code.

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