Many problems are best solved with irregular array structures. These are aggregations not having a rectangular shape. To motivate, here's one example,
Irregularity here changes an O(N^3) solution to O(N). (The file format is a 7zip archive with a MathReader file inside, readable in Windows or Unix with free software.)
These cases also arise in simulations where physical geometry determines array shape. Here memory consumption is the minimization goal that makes irregularity desirable. The access function will return NaN or zero for out-of-bounds requests. There is no need to consume memory storing NaNs and zeros
Please advise how much support numpy/Scipy has for these structures, if any, including future plans. If support exists, could you kindly supply a Scipy declaration matching the first example.
SciPy has sparse matrix support (scipy.sparse) with several storage formats
You can also construct irregular arrays using arrays of objects or just lists of lists.