I'm more interested in what parts of Python are 'accidentally slow' or 'accidentally huge' that Python noobs fall into. I remember when I was first learning Pe

I'm more interested in what parts of Python are 'accidentally slow' or 'accidentally huge' that Python noobs fall into. I remember when I was first learning Perl many years ago, and discovered that certain varieties of looping on an array (most, in fact) actually created a second copy of the array at the start of the loop. This was memory-catastrophic for certain things I was attempting to do, and was easily avoided, but I didn't know it was happening until a Perl monk explained it. What are some similar pitfalls in Python?