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
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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...
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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, 2024Why does Python's eval(input("Enter input: ")) change input's datatype? - Stack Overflow
>>> x = eval('input("Enter a number: ")') Enter a number: 5 >>> x '5' # Here you get a str ... Sign up to request clarification or add additional context in comments. ... Because a number is a valid expression in Python, and it evaluates to itself (and its type is int). More on stackoverflow.com
Demo 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, 2018What does list(map(int,input().split())) do in python?
Let's break it down: input() gets user input and returns a string, e.g. "1 2 3 4 5" input().split() splits that input on whitespaces, e.g. ["1", "2", "3", ...] int() converts a string to a integer, e.g. "1" -> 1 map(fn, sequence) applies the function fn to each element in the sequence, e.g. fn(sequence[0]), fn(sequence[1]), ... map(int, input().split()) applies int to each string element in the input, e.g. ["1", "2", "3", ...] -> int("1"), int("2"), ... list() turns any iterator/generator to a list, e.g. int("1"), int("2"), ... => [1, 2, 3, ...] Example: In []: list(map(int, input().split())) Input: 1 2 3 4 5 Out[]: [1, 2, 3, 4, 5] Note: this is the same as, which may be easier to read: In []: [int(n) for n in input().split()] Input: 1 2 3 4 5 Out[]: [1, 2, 3, 4, 5] More on reddit.com
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September 17, 2020Does eval() work with Python 2 vs Python 3 differently?
The function itself works similarly, but Python 2 had a dangerous input() behavior. In Python 2, input() was equivalent to eval(raw_input()), automatically evaluating whatever the user typed. Python 3 fixed this. input() now returns a plain string. You must explicitly call eval() to evaluate it. If you maintain Python 2 code (which you should migrate), use raw_input() instead of input() to avoid unintended code execution.
leanware.co
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How to Use eval() in Python with Examples & Best Practices
What is the performance impact of eval() vs native Python code?
eval() is slower than native code. Each call parses the string, compiles it to bytecode, and then executes. Native code skips the parsing and compilation steps. For a single evaluation, the difference is negligible. But calling eval() in a loop adds measurable overhead.
leanware.co
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How to Use eval() in Python with Examples & Best Practices
Videos
Great Learning
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Learn eval() Function in Python
June 11, 2025 - The eval() function parses the expression passed to it and evaluates it as a Python expression. In other words, it takes a string input, interprets it as a Python expression, and executes it within the program.
Reddit
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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.
Python Geeks
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Python eval() Function with Examples - Python Geeks
October 30, 2021 - In this article, you will be learning ... introduction. The function eval() is a built-in function that takes an expression as an input and returns the result of the expression on evaluation....
Real Python
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Python eval(): Evaluate Expressions Dynamically – Real Python
October 21, 2023 - You can use the built-in Python eval() to dynamically evaluate expressions from a string-based or compiled-code-based input. If you pass in a string to eval(), then the function parses it, compiles it to bytecode, and evaluates it as a Python ...
Programiz
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Python eval()
The use of globals and locals will be discussed later in this article. The eval() method returns the result evaluated from the expression. x = 1 · print(eval('x + 1')) Output · 2 · Here, the eval() function evaluates the expression x + 1 and print() is used to display this value.
GeeksforGeeks
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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.
Codecademy
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Python | Built-in Functions | eval() | Codecademy
July 11, 2025 - The eval() function is a built-in Python function that dynamically evaluates and executes Python expressions from string-based input.
Leanware
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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
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Why does this happen?
x = eval(input("Enter a number: ")) is not the same thing as x = eval('input("Enter a number: ")')
The former first calls input(...), gets a string, e.g. '5' then evaluates it, that's why you get an int, in this manner:
>>> eval('5') # the str '5' is e.g. the value it gets after calling input(...)
5 # You get an int
While the latter (more aligned with what you were expecting), evaluates the expression 'input("Enter a number: ")'
>>> x = eval('input("Enter a number: ")')
Enter a number: 5
>>> x
'5' # Here you get a str
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0
Because a number is a valid expression in Python, and it evaluates to itself (and its type is int). For example, if you input a rubbish string with a non-existing name (say, 'abcdefgh'), a NameError exception will be raised (the exception is raised while evaluating).
Towards Data Science
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Python eval() built-in-function | Towards Data Science
January 20, 2025 - Also if the user wants to evaluate the string into code then can use eval function, because eval function evaluates the string expression and returns the integer as a result. Now you all know the input() takes the user input, but when the user ...
Real Python
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eval() | Python’s Built-in Functions – Real Python
In this example, eval() evaluates the user’s mathematical expression safely by restricting access to built-in functions, minimizing potential security risks. ... In this step-by-step tutorial, you'll learn how Python's eval() works and how to use it effectively in your programs.
Upgrad
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Eval Function () in Python: Usage, Examples & Security Considerations
November 11, 2024 - It is used to evaluate a string as a Python expression and return the result. You can input a list in Python using `eval` by providing a string representation of the list and then evaluating it.
Python Programming
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Eval Module with Python Tutorial
While you can do this, you have to be incredibly careful! list_str = "[1,5,7,8,2]" list_str = eval(list_str) print(list_str) print(list_str[1]) First, we define a string, that carries the syntax of a list. Next, we use eval to evaluate it. Finally, we can show that it has the properties of a Python list. x = input("see this...") check_this_out = eval(input("code:")) Another example, where we allow the user to input the string to be evaluated. The next question is whether or not we can use logic in evaluate.
Python Central
pythoncentral.io › how-to-use-pythons-eval-function
How to Use Python's eval() Function | Python Central
May 16, 2025 - This comprehensive guide explores ... in Python applications. At its core, Python's eval() function evaluates a string as a Python expression and returns the result. Its syntax is straightforward:...
Shiksha
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Python Eval: Exploring the Pros, Cons, and Best Practices for Safe and Secure Usage - Shiksha Online
May 14, 2024 - Python eval is a built-in function that evaluates the specified expression (if the expression is a legal python statement) and returns the result. The eval() function takes a string as input and returns the result of the expression evaluated.
Python documentation
docs.python.org › 3 › library › functions.html
Built-in Functions — Python 3.14.5rc1 documentation
February 27, 2026 - Code objects can be executed by exec() or eval(). source can either be a normal string, a byte string, or an AST object. Refer to the ast module documentation for information on how to work with AST objects. The filename argument should give the file from which the code was read; pass some recognizable value if it wasn’t read from a file ('<string>' is commonly used).
University of Utah
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Making Python interpret the input: eval
First, the input function reads a string of characters from the keyboard, then the eval function operates on that string, and, finally, the result is stored in the variable age. If you use the same procedure to enter your name, as in · then Python expects that what you type follows its rules for a Python string constant.
Python Reference
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eval — Python Reference (The Right Way) 0.1 documentation
Returns a result of the evaluation of a Python expression. ... Required. The arguments are a Unicode or Latin-1 encoded string ... Optional. A dictionary defining the namespace in which the expression is evaluated.