Is it possible to change IPython's pretty printer?

Question

Is it possible to change the pretty printer that IPython uses?

I'd like to switch out the default pretty printer for pprint++, which I prefer for things like nested structures:

In [42]: {"foo": [{"bar": 42}, {"bar": 16}] * 3, "bar": [1,2,3,4,5]}
Out[42]: 
{'bar': [1, 2, 3, 4, 5],
 'foo': [{'bar': 42},
  {'bar': 16},
  {'bar': 42},
  {'bar': 16},
  {'bar': 42},
  {'bar': 16}]}

In [43]: pprintpp.pprint({"foo": [{"bar": 42}, {"bar": 16}] * 5, "bar": [1,2,3,4,5]})
{
    'bar': [1, 2, 3, 4, 5],
    'foo': [
        {'bar': 42},
        {'bar': 16},
        {'bar': 42},
        {'bar': 16},
        {'bar': 42},
        {'bar': 16},
        {'bar': 42},
        {'bar': 16},
        {'bar': 42},
        {'bar': 16},
    ],
}

Answer 1

This can technically be done by monkey-patching the class IPython.lib.pretty.RepresentationPrinter used here in IPython.

This is how one might do it:

In [1]: o = {"foo": [{"bar": 42}, {"bar": 16}] * 3, "bar": [1,2,3,4,5]}

In [2]: o
Out[2]: 
{'bar': [1, 2, 3, 4, 5],
 'foo': [{'bar': 42},
  {'bar': 16},
  {'bar': 42},
  {'bar': 16},
  {'bar': 42},
  {'bar': 16}]}

In [3]: import IPython.lib.pretty

In [4]: import pprintpp

In [5]: class NewRepresentationPrinter:
            def __init__(self, stream, *args, **kwargs):
                self.stream = stream
            def pretty(self, obj):
                p = pprintpp.pformat(obj)
                self.stream.write(p.rstrip())
            def flush(self):
                pass


In [6]: IPython.lib.pretty.RepresentationPrinter = NewRepresentationPrinter

In [7]: o
Out[7]: 
{
    'bar': [1, 2, 3, 4, 5],
    'foo': [
        {'bar': 42},
        {'bar': 16},
        {'bar': 42},
        {'bar': 16},
        {'bar': 42},
        {'bar': 16},
    ],
}

This is a bad idea for a multitude of reasons, but should technically work for now. Currently it doesn't seem there's an official, supported way to override all pretty-printing in IPython, at least simply.

(note: the .rstrip() is needed because IPython doesn't expect a trailing newline on the result)