I once joined a project that had been going on for 5 years with >100K lines of Python. At any given time we had more than 25 programmers. In my two years on the project I never had a problem reading someone else's code - it was great for maintainability. Our project was used by hundreds of engineers on a critical path of a multi-billion dollar project. Anyone who thinks Python doesn't work for serious development doesn't know what they're talking about.