> ("randomly" as in: why is "open file" throwing an exception when file doesn't exist but "find substring" returns -1 when substring doesn't exist?) Because th

> ("randomly" as in: why is "open file" throwing an exception when file doesn't exist but "find substring" returns -1 when substring doesn't exist?) Because there can be lots of ways for `open` to throw an exception (encoding issues, not found, permissions, etc.). The underlying open syscall has 39 error codes. Python adds a few more failure modes atop that. I'd much rather deal with named error conditions than deal with return values -1 through -50. Find substring can only fail in one way.