Virtual Environments: Why Your Projects Keep Breaking Each Other

You install NumPy for Project A. Works great. Six months later you start Project B. It needs a newer version of NumPy with features that did not exist before. You upgrade. Project B works. You go back to Project A. It breaks. The new NumPy version changed something your old code depended on. You downgrade NumPy. Project A works again. Project B breaks. You go in circles. Neither project is stable. Your global Python installation is a mess of conflicting requirements. This is the dependency hell