Adventures in Machine Learning

Mastering Python’s globals() Function: Accessing and Manipulating Symbol Tables

Introduction to Python

globals() Function

Python is a popular programming language used by developers worldwide for web development, data analysis, artificial intelligence, and more. One of the essential features of Python is its ability to handle variables and objects in a more organized manner using symbol tables.

Symbol tables are an essential component of the Python programming language and are used to store information about the variables, objects, and functions used in a program. In this article, we will discuss the Python

globals() function, its syntax, implementation, and practical uses.

Symbol Table and Its Types

Before we dive into the specifics of the Python

globals() function, let us understand what a symbol table is. In Python, a symbol table is a data structure used to store information about the variables, objects, and functions used in a program.

There are two types of symbol tables in Python: global symbol table and local symbol table. The global symbol table stores information about the variables and functions that are defined outside of a function or a class.

On the other hand, the local symbol table stores information about the variables and functions defined within a function or a class.

Python locals() Function

The Python locals() function is another built-in function used to access the local symbol table. The locals() function returns a dictionary containing the variables and their corresponding values in the current local symbol table.

Syntax and Implementation of

globals() Function

Now that we know what symbol tables are and the difference between global and local symbol tables let’s discuss the syntax and implementation of the Python

globals() function.

Syntax of the

globals() function

The syntax of the Python

globals() function is simple. It does not take any parameters and returns a dictionary containing the symbols in the global symbol table.

Here’s the syntax of the Python

globals() function:

“`python

globals()

“`

Example 1: Using

globals() function to display the Global Symbol Table

To display the global variables used in your program, you can use the

globals() function. Here’s an example:

“`python

x = 10

y = “hello”

def my_func():

z = 5

print(

globals())

“`

Output:

“`python

{

‘__name__’: ‘__main__’,

‘__doc__’: None,

‘__package__’: None,

‘__loader__’: ,

‘__spec__’: None,

‘__annotations__’: {},

‘__builtins__’: ,

‘x’: 10,

‘y’: ‘hello’,

‘my_func’:

}

“`

In this example, the function my_func() does not contain any global variables, so the global symbol table only contains the variables x and y.

Example 2: Using

globals() function to display the Local and Global Scope Variables

Let’s see an example that shows how to use the

globals() function to display both local and global scope variables:

“`python

name = “John”

def greet():

message = “Hello, ” + name

print(message)

print(

globals())

greet()

“`

Output:

“`python

{

‘__name__’: ‘__main__’,

‘__doc__’: None,

‘__package__’: None,

‘__loader__’: ,

‘__spec__’: None,

‘__annotations__’: {},

‘__builtins__’: ,

‘name’: ‘John’,

‘greet’:

}

Hello, John

“`

In this example, the name variable is defined outside the function greet(), making it a global scope variable. Hence, the

globals() function shows the name variable in the global symbol table.

The message variable is defined inside the greet() function, making it a local scope variable. As the local variables are a part of the local symbol table, they are not shown in the global symbol table.

Example 3: Modifying and Manipulating Variables using

globals() function

Let’s see an example of how you can modify the global variables using the

globals() function:

“`python

x = 5

def my_func():

global x

x = x + 10

print(x)

print(x)

my_func()

print(x)

“`

Output:

“`python

5

15

“`

In this example, the function my_func() uses the keyword “global” to access the global variable x. The function then updates the value of x and prints it.

The main program then prints the value of x before and after calling the my_func() function.

Conclusion

In this article, we discussed the Python

globals() function, its syntax, implementation, and practical uses. We also learned about symbol tables and their types.

The use of the Python

globals() function can help you access, modify, and manipulate global scope variables in your Python program. With a better understanding of symbol tables and the

globals() function, you can improve your Python coding experience and become a more proficient Python developer.

Expanding Upon Python

globals() Function

Python is a versatile programming language with a wide range of built-in functions that simplify the coding process. One such built-in function is the

globals() function, which is used to access the global symbol table in Python.

In this article, we will delve deeper into the Python

globals() function and its usage, along with symbol tables, their types, and functions, and how they work in Python. Python

globals() Function – Summary

Python

globals() function is a built-in function used to access and manipulate the global symbol table in Python.

The global symbol table stores information about the variables and functions that are defined outside of a function or a class. By using the

globals() function, we can access the global variables and functions and manipulate them, as required.

The syntax of the

globals() function is simple, and it does not take any parameters. It returns a dictionary containing the symbols in the global symbol table.

The global symbol table stores the variables that are declared outside of any function or class and the functions that are defined at the module level. The symbol table of a module is created when the module is imported, and the variables are stored in the symbol table until the module is unloaded.

Python Symbol Tables – Definition and Types

Symbol tables are data structures used to store information about the variables, objects, and functions used in a program. In Python, there are two types of symbol tables: global symbol tables and local symbol tables.

The global symbol table stores information about the variables and functions that are defined outside of a function or a class. The variables that are declared at the module level are stored in the global symbol table.

The global symbol table is created when the module is imported and stores the variables and functions until the module is unloaded. The local symbol table stores information about the variables and functions defined within a function or a class.

The local symbol table is created when a function is called, and the variables and functions are stored in the local symbol table until the function returns.

Python locals() Function

Python also has another built-in function called locals(). The locals() function returns a dictionary containing the variables and their corresponding values in the current local symbol table.

It is used to access the local symbol table and can be useful in debugging and development.

Implementation of Python Globals() Function

To use the

globals() function, you need to call it without any parameters. It returns a dictionary containing all the global symbols.

Here is an example of the use of the

globals() function. “`python

x = 5

y = “Python”

def

my_function():

z = 7

print(

globals())

my_function()

“`

Output:

“`python

{

‘__name__’: ‘__main__’,

‘__doc__’: None,

‘__package__’: None,

‘__loader__’: ,

‘__spec__’: None,

‘__annotations__’: {},

‘__builtins__’: ,

‘x’: 5,

‘y’: ‘Python’,

‘my_function’:

}

“`

In this example, we have defined two global variables x and y and a function named my_function. The function

my_function() contains a local variable z.

When we call the function, it prints the global symbol table using the

globals() function.

Using Python Globals() Function to Modify the Global Variables

The global keyword allows a function to update global variables outside of its local scope. By using the global keyword, you can modify a global variable from inside a function.

Here is an example of how to use the

globals() function to modify the global variable. “`python

x = 5

def

my_function():

global x

x = 10

print(x)

my_function()

print(x)

“`

Output:

“`python

10

10

“`

In this example, we defined a global variable x and a function named my_function. Inside the function, we used the global keyword to modify the value of the global variable x to 10, and we printed the modified value of x inside the function.

Then we printed the value of x again, outside of the function, demonstrating that the global keyword modified the global variable.

Conclusion

In conclusion, the global symbol table stores information about the variables and functions that are defined outside of a function or a class. The Python

globals() function is a built-in function used to access and manipulate the global symbol table in Python.

The use of the

globals() function can help you access, modify, and manipulate global scope variables in your Python program. Meanwhile, the local scope is used to store objects within functions and objects local to a code block.

The Python locals() function allows the user to access the local symbol table and can be useful in debugging and development. Having a firm understanding of the global and local symbol tables and their respective functions can improve your Python coding experience and make you a more efficient Python developer.

References:

1. Python Global Keyword.

(n.d.). Retrieved from https://www.w3schools.com/python/ref_keyword_global.asp

2.

Python Scope and Namespace. (n.d.).

Retrieved from https://www.datacamp.com/community/tutorials/scope-of-variables-python

3. Python Symbols.

(n.d.). Retrieved from https://www.programiz.com/python-programming/symbol-table

In summary, the Python

globals() function is a built-in function used to access and manipulate the global symbol table in Python.

Global and local symbol tables are data structures used to store information about the variables, objects, and functions used in a program. The use of the Python

globals() function can help you access, modify, and manipulate global scope variables in your Python program, while the Python locals() function allows you to access the local symbol table.

Having a firm understanding of the global and local symbol tables and their respective functions can improve your Python coding experience and make you a more efficient Python developer.

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