The BList is a type that looks, acts, and quacks like a Python list, but has better performance for for modifying large lists.
For small lists (fewer than 128 elements), BLists and the built-in list have very similar performance.
>>> from blist import *
>>> x = blist() # x is a BList with one element
>>> x *= 2**29 # x is a BList with > 500 million elements
>>> x.append(5) # append to x
>>> y = x[4:-234234] # Take a 500 million element slice from x
>>> del x[3:1024] # Delete a few thousand elements from x