Re Windows 95, thanks for the correction, I'll update the root node. It seems that Windows NT was a rewrite of Windows 3 and that Windows 95 was derived from the Windows 3 code base.

Python 3: I only claimed it was meeting "substantial resistance". Maybe that's unfair, depending on your interpretation of "substantial", but it's certainly meeting some resistance based on random web chatter on the subject. Well, I'm a Python user and I'm resisting it. ;-) My personal opinion is that breaking backward compatibility was unwarranted for a release with relatively modest improvements. Many businesses with large investments in Python 2.x code will resist Python 3 indefinitely because upgrading will prove too risky and/or too expensive.

Update (2017): Even a company as wealthy as Google, according to this Hacker News item, are still heavily using Python 2. This is hardly surprising. Where is the ROI on spending millions of dollars rewriting millions of lines of already working code, without adding any customer value, while being almost guaranteed to suffer numerous breakages to critical business systems? You also pay an Opportunity cost. Curiously, I see some of Google's legacy Python 2 systems are being rewritten in Go perhaps because at least there is some perceived customer value (faster performance) in a Go rewrite. For smaller less wealthy companies, rewriting millions of lines of working Python 2 code in Python 3 could well put them out of business. Of course, if you don't have much Python 2 code, switching to Python 3 is a no brainer.

Update (2020): I see Jython is still Python 2 and IronPython3 unfinished. At least Perl doesn't have to worry about updating Java and CLR versions of the language. :)

Update (2023): Despite (or perhaps because ;-) it abandoned its many Python 2 users, Python won the language adoption war, at least it's now No. 1 in the TIOBE index. This topic is analysed in more detail at Organizational Culture (Part VI): Sociology.

See Also

• Martian Headsets by Joel (on breaking compatibility)
• How Microsoft lost the API war by Joel
• Robustness Principle (sadly Postel's Law "Be conservative in what you send, be liberal in what you accept" is double-edged)

• Improving p5p: Perl is going to stay Perl (and Stroustrup quote in this reply) (June 2021)
• I failed today by erickp (April 2023)