How to python eval in C++

The Python eval() function is a built-in function that evaluates a string as a Python expression. It takes a string as an argument and returns the result of the expression. The expression can be a simple arithmetic operation or a complex function call. The eval() function is useful when you need to dynamically evaluate a string as a Python expression at runtime. However, it is important to use the eval() function with caution as it can execute arbitrary code and potentially introduce security vulnerabilities if used improperly.. Keep reading below to learn how to python eval in C++.

Python ‘eval’ in C++ With Example Code

Python’s `eval()` function is a powerful tool for evaluating expressions and executing code dynamically. If you’re working with C++, you may be wondering if there’s a way to use `eval()` in your code. Fortunately, there is a way to do this using the `pybind11` library.

`pybind11` is a lightweight header-only library that provides a simple way to expose C++ code to Python. With `pybind11`, you can create Python modules that wrap your C++ code and make it accessible from Python.

To use `eval()` in C++ using `pybind11`, you’ll need to follow a few steps:

1. Install `pybind11` using your preferred package manager or by downloading the source code from the `pybind11` GitHub repository.

2. Create a new C++ file and include the `pybind11` header:

“`cpp
#include “`

3. Define a function that takes a string argument and returns the result of calling `eval()` on that string:

“`cpp
int eval(const std::string& expr) {
pybind11::gil_scoped_acquire acquire;
return pybind11::eval(expr);
}
“`

4. Use `PYBIND11_MODULE` to create a Python module that exposes the `eval()` function:

“`cpp
PYBIND11_MODULE(pyeval, m) {
m.def(“eval”, &eval, “Evaluate a Python expression”);
}
“`

5. Compile your code into a shared library and load it into Python using `importlib`:

“`python
import importlib
import os

# Load the shared library
lib = importlib.machinery.ExtensionFileLoader(
‘pyeval’, os.path.abspath(‘pyeval.so’)).load_module()

# Call the eval function
result = lib.eval(‘2 + 2’)
print(result) # Output: 4
“`

With these steps, you can now use `eval()` in your C++ code and call it from Python. Keep in mind that using `eval()` can be dangerous if you’re not careful, as it allows arbitrary code execution. Make sure to validate any input before passing it to `eval()`.

Equivalent of Python eval in C++

In conclusion, the equivalent function to Python’s eval() in C++ is the std::eval() function. This function allows C++ programmers to evaluate and execute code dynamically at runtime, just like the eval() function in Python. However, it is important to note that the std::eval() function is only available in C++17 and later versions. Additionally, it is important to use this function with caution as it can potentially introduce security vulnerabilities if not used properly. Overall, the std::eval() function is a powerful tool for C++ programmers who need to execute code dynamically and can be a valuable addition to their programming toolkit.