Dynamic execution of python code by using string or code object

exec(object, global,local ) execute valid python code

object: input object of string or code object
global: (optional ) global dictionary object
local: (optional ) local dictionary object

Return : The return value is None.

Using string object

my_str="x='plus2net'\nprint(x)"
exec(my_str)

Output

plus2net

Using code object

We create a code object by using compile()

cb=compile('print("Hello")', '', 'single')
exec(cb)

Output

Hello

Using restrictions

We can allow some functions in global scope only to execute by using global option. Let us import our math module and find the sum of a iterable_object This will generate error as we have used one empty dictionary ( not allowing any method ) .

import math
str="print(math.fsum([1,2,3,4,5]))"
exec(str,{})

This will work as we have allowed math.fsum to execute. Output is 15.0

import math
str="print(fs([1,2,3,4,5]))"
exec(str,{"fs":math.fsum}) # 15.0

builtin functions

exec() has full access to all builtin functions of Python. This code will not generate any error though we have supplied an empty dictionary ({}) to globals. Output is 15

str="print(sum([1,2,3,4,5]))"
exec(str,{})  # 15

Difference Between eval() and exec() in Python

eval() is used to evaluate a single Python expression and return the result. It's suitable for simple evaluations of Python expressions that have a return value.

exec() is used for executing dynamically generated Python code which can be more complex than a single expression. It can execute multiple statements and even complex code structures, such as loops or function definitions, but it doesn't return the result.

Take precaution by not allowing un-cleaned code to get executed through exec(). There is a potential danger in allowing codes to get executed without proper check.

All Built in Functions in Python dir() eval() compile()

Math Functions math.fabs() Python- Tutorials

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

About the author Watch on YouTube

Connect:

Subscribe to our YouTube Channel here

exec(): dynamically executes Python code