fix(security): 2 improvements across 2 files

[tomaioo]

Summary

fix(security): 2 improvements across 2 files

Problem

Severity: Medium | File: src/openfermion/chem/reduced_hamiltonian.py:L48

In make_reduced_hamiltonian, the function calculates normalization = 1 / (4 * (n_electrons - 1)) without validating that n_electrons > 1. If n_electrons is 1, this causes a ZeroDivisionError. Additionally, if n_electrons is 0 or negative, the behavior is undefined and could lead to incorrect scientific results.

Solution

Add input validation at the beginning of the function to ensure n_electrons >= 2, raising a ValueError with a descriptive message if not. Consider also validating that n_electrons is a positive integer.

Changes

• src/openfermion/chem/reduced_hamiltonian.py (modified)
• src/openfermion/linalg/rdm_reconstruction.py (modified)

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[gemini-code-assist]

Code Review

This pull request introduces validation checks to ensure that n_electrons is at least 2 in both make_reduced_hamiltonian and valdemoro_reconstruction to prevent division by zero. However, in make_reduced_hamiltonian, the validation check was placed before the docstring, which prevents Python from recognizing it as a docstring and breaks documentation generation. This check should be moved after the docstring.

[gemini-code-assist]

In Python, a function's docstring must be the very first statement in the function body. Placing the if n_electrons < 2: validation check before the docstring prevents Python from recognizing it as a docstring, which breaks documentation generation and tools. Please move this validation block to be after the docstring (after line 39).