The problem with Python strings is that innocuous operations can occasionally cause drastic memory usage ballooning. A simple string append can, for instance,

The problem with Python strings is that innocuous operations can occasionally cause drastic memory usage ballooning. A simple string append can, for instance, require up to 5x the memory consumed by the string. Worse, this problem will only show up if someone ever enters in a high enough code point. Better hope any user-defined data never gets turned into part of a large string at any point, or you have a potential memory problem down the line.