[FIXED] What does KeyError: 'text/plain' mean?

Issue

I got this error while playing around after reading Guido's blog "Tail Recursion Elimination."

I was curious if there was a non-recursive limitation on nested dictionaries and, I did get an error message but only under a very specific circumstance using an IPython console.

There is no error if I lower the xrange (100 works). What's going on here?

thing = {}
thing2 = thing
for x in xrange(500):
    thing2[x] = {}
    thing2 = thing2[x]

thing

output:

Traceback (most recent call last):

  File "<ipython-input-83-0b6d347b01d4>", line 1, in <module>
    thing

  File "C:\Python27\lib\site-packages\IPython\core\displayhook.py", line 255, in __call__
    self.log_output(format_dict)

  File "C:\Python27\lib\site-packages\IPython\core\displayhook.py", line 227, in log_output
    format_dict['text/plain']

KeyError: 'text/plain'


repr(thing)
Out[84]: '{0: {1: {2: {3: {4: ....{497: {498: {499: {}}}}}}}}'

Solution

It definitely is an IPython issue. If you try to display the "thing", it fails (in Python3 / IPython 4 with another error message). However, it is perfectly valid object.

This (5 million levels) is ok (although it takes a few seconds to create):

thing = {}
thing2 = thing
for x in range(5000000):
    thing2[x] = {}
    thing2 = thing2[x]
thing;

Answered By - honza_p