+ 1 for easy serialization. Every language should have equivalent of Python pickle module.
Sometimes you need specific file format, compatibility between languages, customization, etc - then pickle is not enough. But for my uses pickle was good enough most of the time, and it's stupidly easy to use. No need to change your code in any way. That makes one-off cashing of intermediate results to file system manageable, implementing save/load game is 3 lines of code (counting import). I love it, and I miss it in every other language I use.
Javascript has JSON, but writing general code to serialize arbitrary object graph with cycles, functions as field values, properly storing prototype chains, etc is still hard.
Sometimes you need specific file format, compatibility between languages, customization, etc - then pickle is not enough. But for my uses pickle was good enough most of the time, and it's stupidly easy to use. No need to change your code in any way. That makes one-off cashing of intermediate results to file system manageable, implementing save/load game is 3 lines of code (counting import). I love it, and I miss it in every other language I use.
Javascript has JSON, but writing general code to serialize arbitrary object graph with cycles, functions as field values, properly storing prototype chains, etc is still hard.