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"""Utilities to manipulate JSON objects.
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"""
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#-----------------------------------------------------------------------------
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# Copyright (C) 2010 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING.txt, distributed as part of this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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# stdlib
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import types
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#-----------------------------------------------------------------------------
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# Classes and functions
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#-----------------------------------------------------------------------------
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def json_clean(obj):
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"""Clean an object to ensure it's safe to encode in JSON.
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Atomic, immutable objects are returned unmodified. Sets and tuples are
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converted to lists, lists are copied and dicts are also copied.
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Note: dicts whose keys could cause collisions upon encoding (such as a dict
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with both the number 1 and the string '1' as keys) will cause a ValueError
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to be raised.
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Parameters
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----------
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obj : any python object
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Returns
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-------
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out : object
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A version of the input which will not cause an encoding error when
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encoded as JSON. Note that this function does not *encode* its inputs,
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it simply sanitizes it so that there will be no encoding errors later.
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Examples
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--------
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>>> json_clean(4)
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4
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>>> json_clean(range(10))
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[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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>>> json_clean(dict(x=1, y=2))
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{'y': 2, 'x': 1}
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>>> json_clean(dict(x=1, y=2, z=[1,2,3]))
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{'y': 2, 'x': 1, 'z': [1, 2, 3]}
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>>> json_clean(True)
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True
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"""
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# types that are 'atomic' and ok in json as-is. bool doesn't need to be
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# listed explicitly because bools pass as int instances
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atomic_ok = (basestring, int, float, types.NoneType)
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# containers that we need to convert into lists
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container_to_list = (tuple, set, types.GeneratorType)
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if isinstance(obj, atomic_ok):
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return obj
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if isinstance(obj, container_to_list) or (
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hasattr(obj, '__iter__') and hasattr(obj, 'next')):
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obj = list(obj)
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if isinstance(obj, list):
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return [json_clean(x) for x in obj]
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if isinstance(obj, dict):
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# First, validate that the dict won't lose data in conversion due to
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# key collisions after stringification. This can happen with keys like
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# True and 'true' or 1 and '1', which collide in JSON.
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nkeys = len(obj)
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nkeys_collapsed = len(set(map(str, obj)))
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if nkeys != nkeys_collapsed:
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raise ValueError('dict can not be safely converted to JSON: '
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'key collision would lead to dropped values')
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# If all OK, proceed by making the new dict that will be json-safe
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out = {}
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for k,v in obj.iteritems():
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out[str(k)] = json_clean(v)
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return out
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# If we get here, we don't know how to handle the object, so we just get
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# its repr and return that. This will catch lambdas, open sockets, class
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# objects, and any other complicated contraption that json can't encode
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return repr(obj)
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