The eval function lets a Python program run Python code within itself.
eval example (interactive shell):
>>> x = 1
>>> eval('x + 1')
2
>>> eval('x')
1
W3Schools
w3schools.com › python › ref_func_eval.asp
Python eval() Function
Python Examples Python Compiler ... Python Interview Q&A Python Bootcamp Python Training ... The eval() function evaluates the specified expression, if the expression is a legal Python statement, it will be executed...
Top answer 1 of 12
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The eval function lets a Python program run Python code within itself.
eval example (interactive shell):
>>> x = 1
>>> eval('x + 1')
2
>>> eval('x')
1
2 of 12
185
eval() interprets a string as code. The reason why so many people have warned you about using this is because a user can use this as an option to run code on the computer. If you have eval(input()) and os imported, a person could type into input() os.system('rm -R *') which would delete all your files in your home directory. (Assuming you have a unix system). Using eval() is a security hole. If you need to convert strings to other formats, try to use things that do that, like int().
Valid uses of eval()?
Writing a REPL is one. This includes tools like IPython remote core and Jupyter Notebook. The werkzeug debugger allows you to run arbitrary code to inspect stack traces. More on reddit.com
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March 1, 2024How to use the eval() function
Don't. You never need it, but you certainly don't need it here. Describe what you're trying to achieve here, what specific rule one should follow to get from the string to the desired list. More on reddit.com
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September 6, 2024Demo of how input() is security probem in Python 2.7 (4min)
Demo of how writing insecure code is a security problem. More on reddit.com
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March 15, 2018eval python - beginner
Eval can also work on code objects (for that read the eval() documentation . What eval does is evaluate the code in the string in the context (global and local scope) it is used. So it recognizes the x in your string as the variable x, the + as the plus-operator and the '1' as the integer value 1. Then it executes or evaluates this findings. All this is also explained in the documentation linked above. Or am I missing what you are asking? More on reddit.com
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January 7, 2016Videos
GeeksforGeeks
geeksforgeeks.org › python › eval-in-python
eval in Python - GeeksforGeeks
July 23, 2025 - Python eval function comes with the facility of explicitly passing a list of functions or variables that it can access. We need to pass it as an argument in the form of a dictionary. ... from math import * def secret_function(): return "Secret key is 1234" def function_creator(): # expression to be evaluated expr = input("Enter the function(in terms of x):") # variable used in expression x = int(input("Enter the value of x:")) # passing variable x in safe dictionary safe_dict['x'] = x # evaluating expression y = eval(expr, {}, safe_dict) # printing evaluated result print("y = {}".format(y)) if
Great Learning
mygreatlearning.com › blog › it/software development › eval() function in python
Learn eval() Function in Python
June 11, 2025 - The eval() function sees x and y from the surrounding code and uses their values. Using eval() to calculate mathematical formulas from text is a great way to build tools that work like Excel calculators. However, even simple math in Python relies on a solid grasp of how numbers and strings interact.
Udacity
udacity.com › blog › 2023 › 03 › pythons-eval-the-most-powerful-function-you-should-never-use.html
Python’s eval(): the most powerful function you should never use. | Udacity
March 22, 2023 - Back Python’s eval(): the most powerful function you should never use. ... eval() is a simple and powerful function built into Python’s interpreter. As the name implies, the function *evaluates* whatever expression is passed to it.
Real Python
realpython.com › python-eval-function
Python eval(): Evaluate Expressions Dynamically – Real Python
October 21, 2023 - The signature of Python’s eval() is defined as follows: ... The function takes a first argument, called expression, which holds the expression that you need to evaluate. eval() also takes two optional arguments: ... In the next three sections, you’ll learn what these arguments are and how eval() uses them to evaluate Python expressions on the fly.
Codecademy
codecademy.com › docs › python › built-in functions › eval()
Python | Built-in Functions | eval() | Codecademy
July 11, 2025 - This powerful function parses a string containing a Python expression, compiles it into bytecode, and then evaluates it as if it were written directly in the code. The eval() function is commonly used in scenarios where there is a need to evaluate mathematical expressions from user input, create dynamic code execution systems, or process expressions stored as strings.
Programiz
programiz.com › python-programming › methods › built-in › eval
Python eval()
Dictionary is the standard and commonly used mapping type in Python. The use of globals and locals will be discussed later in this article. The eval() method returns the result evaluated from the expression. ... Here, the eval() function evaluates the expression x + 1 and print() is used to ...
Reddit
reddit.com › r/python › valid uses of eval()?
r/Python on Reddit: Valid uses of eval()?
March 1, 2024 -
I’m wondering if anyone has ever seen a case of code using eval() and thought to themselves “yeah actually that’s probably the right way to do it”?
My understanding has always been that it’s a huge security risk and generally a recipe for disaster.
But I was just working on a task where I couldn’t really figure out any other way to achieve the dynamic functionality I was looking for, so I wrote code that assembles a string to do what I need, and then runs eval() on that string. Pretty sure this is the first time I’ve ever used eval() at all.
It’s a low-stakes proof of concept for a totally internal tool, so I’m not hugely worried about security at the moment, but it just feels so icky to do something like that. I’m curious if in others’ experience there’s always a better way than using eval(), or if sometimes it’s legit.
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Writing a REPL is one. This includes tools like IPython remote core and Jupyter Notebook. The werkzeug debugger allows you to run arbitrary code to inspect stack traces.
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Not eval(), but I've used exec() to quickly create a Domain Specific Language. With exec(), you have complete control of the globals and locals of the execution context. I removed all of python "built-in" methods from the globals, which essentially "sandboxed" the execution context, preventing the code I exec() from doing anything but calling the functions I explicitly installed into the context. I have no idea if this "sandbox" was actually secure, but it was good enough for my usecase. You can see my code here: https://gist.github.com/phire/993aad1cee3a081028db5d364d7110c0 It worked great as a quick and dirty experiment to solve a problem, and I'm not sure it's a good idea or not for a production ready project. But that's mostly because I probably don't need to do any sandboxing at all, or I should be going all in and creating a DSL from scratch.
Real Python
realpython.com › ref › builtin-functions › eval
eval() | Python’s Built-in Functions – Real Python
The built-in eval() function allows you to dynamically evaluate Python expressions from a string or compiled code object and returns the result of the evaluated expression: ... Note: If locals isn’t provided, then it defaults to globals.
DataFlair
data-flair.training › blogs › python-eval-function
Python eval Function - Examples & Uses - DataFlair
August 27, 2018 - In this eval function in Python example, we initialize x to 7. We then pass a string to eval that, we expect, will square the value of x and stuff it into x. We see that it works fine. eval in Python evaluates the expression x**2 to get to the value 49 and then prints it. Now, let’s try another Python eval() example. ... This converts the string to the list [2,3,4] and returns the value at position 1, that is, 3.However, eval() in Python does not compile, only evaluates:
Medium
medium.com › @nikomanousos123 › exploiting-pythons-eval-function-69f8fc4074a1
Exploiting Python’s Eval Function | by Niko | Medium
July 7, 2025 - What is eval? Eval is a built-in Python function. If you are new to Python, a built-in function is a function that is pre-built into the language, and you don’t need to import extra headers or libraries to use it. Eval works by taking a string argument, and will evaluate it and return the result.
Towards Data Science
towardsdatascience.com › home › latest › python eval() built-in-function
Python eval() built-in-function | Towards Data Science
January 20, 2025 - In simple words, the eval function evaluates the "String" like a python expression and returns the result as an integer. The syntax of the eval function is as shown below:
Tutorialspoint
tutorialspoint.com › python › python-eval-function.htm
Python eval() Function
The Python eval() function is a built-in function used to evaluate a string as a Python expression and return the result. It takes a string containing a valid Python expression as input, parses it, and execute the code, ultimately returning the
Leanware
leanware.co › insights › how-to-use-eval-in-python
How to Use eval() in Python with Examples & Best Practices
Automated Trading Platform Dev for Algorithmic Trading Co
This makes it useful for dynamic expression evaluation, but also dangerous if you pass untrusted input.Most Python developers encounter eval() when building calculators, processing configuration files, or working with dynamic code generation. The function does exactly what it promises, which is ... Leanware has a good working process and iterates on the product quickly, adapting to the client’s methodologies. The team is accommodating with the timeline and communicates effectively through thrice-weekly phone calls, Slack, and reports. Their flexibility has made them an excellent partner. Learn
PrepBytes
prepbytes.com › home › python › python eval function
Python Eval Function
October 30, 2023 - The eval() function in Python is a built-in function that evaluates a string as a Python expression and returns the result.
YouTube
youtube.com › sentdex
Python Eval programming tutorial - YouTube
The expression argument is parsed and evaluated as a Python expression (technically speaking, a condition list) using the globals and locals dictionaries as ...
Published May 23, 2015 Views 39K
Python Geeks
pythongeeks.org › python geeks › learn python › python eval() function with examples
Python eval() Function with Examples - Python Geeks
October 30, 2021 - Though this function is rarely used due to its vulnerabilities, it has its applications which include: 1. Allowing the user to give their scriptlets that can be used for customizing the complex systems. 2. Evaluating mathematical expressions more easily compared to writing an expression parser. Q1. Write a program to print the result of 4 to the power of 3 using the eval function. Ans. Below is the example of Python eval():
Toppr
toppr.com › guides › python-guide › references › methods-and-functions › methods › built-in › eval › python-eval
Python eval() | What is Python eval() function? | When is eval() used?
August 18, 2021 - Programmers can use the Python eval() function to dynamically evaluate expressions passed as a string argument to the built-in function. When a string is passed to Python eval(), it is parsed, compiled to bytecode, and then evaluated as a Python expression.
ThePythonGuru
thepythonguru.com › python-builtin-functions › eval
Python eval() function - ThePythonGuru.com
The eval() allows us to execute arbitrary strings as Python code. It accepts a source string and returns an object.Its syntax is as follows:Syntax:ev…