Dynamic evalution of python code by using string or code object

eval(object, global,local ) evalute valid python code

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

Using string object

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

Output

plus2net

Using code object

We create a code object by using compile()

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

Output

Hello

my_result = eval('2 + 4')
print(my_result) # Output is 6

Using restrictions

We can allow some functions in global scope only to evalute 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
my_str="print(math.fsum([1,2,3,4,5]))"
eval(my_str,{})

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

import math
my_str="print(fs([1,2,3,4,5]))"
eval(my_str,{'fs':math.fsum}) 3 15.0

builtin functions

eval() 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.

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

Note that sum() is a builtin function but fsum() is included in math module.
Difference Between eval() and exec()

Caution When Using eval()

While eval() is a powerful function, it poses significant security risks if used with unvalidated or untrusted input. Executing dynamically generated code can lead to vulnerabilities, such as code injection attacks. Always validate or sanitize inputs when using eval(), or avoid it in scenarios involving untrusted sources.

All Built in Functions in Python dir() compile() exec() repr()

Math Functions math.fabs() Python- Tutorials

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eval(): executes a specified expression string as Python code

Using string object

Using code object

Using restrictions

builtin functions

Caution When Using eval()

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