This repository contains Python code developed to fit quasar (QSO) spectra using several emission/profile models — Gaussian, Linear, Quadratic, and Cubic. The code reads QSO spectra and fits emission profiles to help analyze line properties and continuum shapes. Reference (Dong et al. (2008). Preprint: arXiv:0710.1458 — https://arxiv.org/pdf/0710.1458). (Original published version: Dong et al., Mon. Not. R. Astron. Soc. 383, 581–592 (2008).)