Global

Definition

The term 'global' in programming refers to the scope or visibility of a variable. A global variable is a variable that is accessible throughout the entire program, regardless of the function or block of code it is defined in.

5 Must Know Facts For Your Next Test

1. Global variables can be accessed and modified from any part of the program, including within functions.
2. Using global variables can make code more difficult to understand and maintain, as the value of a variable can be changed unexpectedly from any part of the program.
3. Global variables should be used sparingly, as they can lead to unintended side effects and make the code more prone to bugs.
4. In Python, the 'global' keyword is used to declare a variable as global within a function, allowing it to be accessed and modified.
5. Overuse of global variables can lead to a phenomenon called the 'global state', which can make the code harder to reason about and test.

Review Questions

• Explain how global variables differ from local variables in terms of scope and accessibility.
  • Global variables are accessible throughout the entire program, while local variables are only accessible within the function or block of code where they are defined. Global variables can be accessed and modified from any part of the program, whereas local variables have a more limited scope and can only be used within their defined context. This difference in scope and accessibility can have significant implications for the organization and maintainability of code, as global variables can introduce unintended side effects and make the code more prone to bugs.
• Describe the potential drawbacks of using global variables in a program and explain why they should be used sparingly.
  • Global variables can make code more difficult to understand and maintain, as their values can be changed unexpectedly from any part of the program. This can lead to unintended side effects and make the code more prone to bugs. Additionally, the overuse of global variables can contribute to a phenomenon called the 'global state', which can make the code harder to reason about and test. As a result, it is generally recommended to use global variables sparingly and instead focus on using local variables and function parameters to encapsulate data and functionality within their appropriate contexts.
• Analyze the role of the 'global' keyword in Python and explain how it can be used to access and modify global variables within a function.
  • In Python, the 'global' keyword is used to declare a variable as global within a function, allowing it to be accessed and modified. This is necessary because, by default, variables defined within a function are considered local to that function, and any attempt to modify a global variable from within a function will create a new local variable with the same name. By using the 'global' keyword, the programmer can explicitly indicate that the variable being accessed or modified is the global variable, rather than a local variable. However, the overuse of global variables and the 'global' keyword can lead to code that is harder to understand, maintain, and test, so it is generally recommended to use them sparingly and focus on other programming practices, such as using function parameters and return values, to manage data and functionality.

Related terms

Scope: The scope of a variable determines where it can be accessed and modified within a program.

Local Variable: A variable that is only accessible within the function or block of code where it is defined.

Namespace: A way to organize and group related variables, functions, and other programming elements to avoid naming conflicts.