Old Python handled strings in a really dumb way that only seemed to work for monolingual Americans and (to a lesser extent) Western Europeans. New Python fixed

Old Python handled strings in a really dumb way that only seemed to work for monolingual Americans and (to a lesser extent) Western Europeans. New Python fixed that. Problems: 1) new Python wasn't very tolerant of real-world conditions where incorrect text encoding happens once in a while. 1b) there was great resistance to fixing that because "Python now did it correctly!" and the rest of the world was just assumed to do it correctly, always. 2) not everybody who already programmed in Python really understood the need for the new (and mostly correct) way of handling strings. Also not everybody in the US really understood Unicode and encodings. 3) there was no proper update path from Old Python to New Python. 4) it was not possible (or very difficult) to write code that was both valid Old Python and valid New Python and which did the right thing in both cases. 5) at the same time the interface for libraries written in C was changed. 5a) the new way was better. 5b) a change was needed for New Pythons string handling anyway. 5c) it could still have been done in a backwards-compatible way... 5d) ... but it wasn't, since the new way was Better. 6) lots of important Python libraries are partially written in C because pure Python is so slow 7) ... so porting all the important libraries was necessary for New Python to take off while at the same time being rather annoying and difficult work. There were other changes at the same time that were improvements but which made upgrading hard. Print was no longer a keyword with lots of special handling and corner cases but an ordinary function. You could switch newer versions of Python 2.x to the same behaviour but not the older ones. Many libraries needed to work with many different Python 2.x versions, which made it hard to support Python 3.x at the same time. You could convert all your print statements to using a function that worked like the new print function and then either use that natively (3.x and newer 2.x) or provide a compatibility function that wrapped the print statement (older 2.x). You would put this code in a module you would selectively import depending on the Python version -- or some variant of that. Not actually hard but really annoying and something that required changing many lines of some libraries. Ad 1, things have improved a lot and there are now known ways of fixing the remaining problems (with newer 3.x versions). Ad 2, Unicode is better understood these days. Ad 3 and 4, things have again improved. If you skip the first few 3.x versions and the early 2.x versions then it is not too hard to write code that works on both Old and New Python. Ad 5, I don't know if is possible to support both ABIs in a single shared library, but at least the core code that actually does the work can be shared. PyPy might have helped as well by making ordinary Python -- the kind you would otherwise write in C -- run fast. Edit: formatting is hard.