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:
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:
x = 10
y = "hello"
def my_func():
z = 5
print(globals())
Output:
{
'__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:
name = "John"
def greet():
message = "Hello, " + name
print(message)
print(globals())
greet()
Output:
{
'__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:
x = 5
def my_func():
global x
x = x + 10
print(x)
print(x)
my_func()
print(x)
Output:
5
15
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:
{
'__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:
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.