Safely viewing lists in ipython

Question

When I ask an ipython notebook to display (via evaluate) a large np.array ipython uses ellipses to summarize the data. However if I ask ipython to display a large list, no such safe guard is in place and my poor ipython notebook struggles. Are there any magics or other tools I can use? I run an ipython notebook in emacs.

Answer 1

What you want is to add display support to existing object (example with polynomial and TeX) (those you can't tamper the source with) what you are trying to define is a "pretty Formatter" (aka _repr_pretty_) for those. You will have a difficulty compared to numpy arrays which is that list are heterogeneous, and so the first element can be a really supper long element.

You can also look at the plain doc for existing formatters, to get an idea.

Answer 2

could you not just test the length of the list yourself? Or wrap the lists as generators?

>>> def guard(XS,N):
...     if len(XS) > N:
...         return "list too long" # or whatever you want
...     else:
...         return XS
... 
>>> guard([1,2,3,4],2)
'list too long'
>>> guard([1,2,3,4],6)
[1, 2, 3, 4]
>>>