Any way to properly pretty-print ordered dictionar

Question

I like the pprint module in Python. I use it a lot for testing and debugging. I frequently use the width option to make sure the output fits nicely within my terminal window.

It has worked fine until they added the new ordered dictionary type in Python 2.7 (another cool feature I really like). If I try to pretty-print an ordered dictionary, it doesn't show nicely. Instead of having each key-value pair on its own line, the whole thing shows up on one long line, which wraps many times and is hard to read.

Does anyone here have a way to make it print nicely, like the old unordered dictionaries? I could probably figure something out, possibly using the PrettyPrinter.format method, if I spend enough time, but I am wondering if anyone here already knows of a solution.

UPDATE: I filed a bug report for this. You can see it at http://bugs.python.org/issue10592.

Answer 1

You could redefine pprint() and intercept calls for OrderedDict's. Here's a simple illustration. As written, the OrderedDict override code ignores any optional stream, indent, width, or depth keywords that may have been passed, but could be enhanced to implement them. Unfortunately this technique doesn't handle them inside another container, such as a list of OrderDict's

from collections import OrderedDict
from pprint import pprint as pp_pprint

def pprint(obj, *args, **kwrds):
    if not isinstance(obj, OrderedDict):
        # use stock function
        return pp_pprint(obj, *args, **kwrds)
    else:
        # very simple sample custom implementation...
        print "{"
        for key in obj:
            print "    %r:%r" % (key, obj[key])
        print "}"

l = [10, 2, 4]
d = dict((('john',1), ('paul',2), ('mary',3)))
od = OrderedDict((('john',1), ('paul',2), ('mary',3)))
pprint(l, width=4)
# [10,
#  2,
#  4]
pprint(d)
# {'john': 1, 'mary': 3, 'paul': 2}

pprint(od)
# {
#     'john':1
#     'paul':2
#     'mary':3
# }

Answer 2

I've tested this unholy monkey-patch based hack on python3.5 and it works:

pprint.PrettyPrinter._dispatch[pprint._collections.OrderedDict.__repr__] = pprint.PrettyPrinter._pprint_dict


def unsorted_pprint(data):
    def fake_sort(*args, **kwargs):
        return args[0]
    orig_sorted = __builtins__.sorted
    try:
        __builtins__.sorted = fake_sort
        pprint.pprint(data)
    finally:
        __builtins__.sorted = orig_sorted

You make pprint use the usual dict based summary and also disable sorting for the duration of the call so that no keys are actually sorted for printing.