问题
How can I test whether two JSON objects are equal in python, disregarding the order of lists?
For example ...
JSON document a:
{
"errors": [
{"error": "invalid", "field": "email"},
{"error": "required", "field": "name"}
],
"success": false
}
JSON document b:
{
"success": false,
"errors": [
{"error": "required", "field": "name"},
{"error": "invalid", "field": "email"}
]
}
a and b should compare equal, even though the order of the "errors" lists are different.
回答1:
If you want two objects with the same elements but in a different order to compare equal, then the obvious thing to do is compare sorted copies of them - for instance, for the dictionaries represented by your JSON strings a and b:
import json
a = json.loads("""
{
"errors": [
{"error": "invalid", "field": "email"},
{"error": "required", "field": "name"}
],
"success": false
}
""")
b = json.loads("""
{
"success": false,
"errors": [
{"error": "required", "field": "name"},
{"error": "invalid", "field": "email"}
]
}
""")
>>> sorted(a.items()) == sorted(b.items())
False
... but that doesn't work, because in each case, the "errors" item of the top-level dict is a list with the same elements in a different order, and sorted() doesn't try to sort anything except the "top" level of an iterable.
To fix that, we can define an ordered function which will recursively sort any lists it finds (and convert dictionaries to lists of (key, value) pairs so that they're orderable):
def ordered(obj):
if isinstance(obj, dict):
return sorted((k, ordered(v)) for k, v in obj.items())
if isinstance(obj, list):
return sorted(ordered(x) for x in obj)
else:
return obj
If we apply this function to a and b, the results compare equal:
>>> ordered(a) == ordered(b)
True
回答2:
Another way could be to use json.dumps(X, sort_keys=True) option:
import json
a, b = json.dumps(a, sort_keys=True), json.dumps(b, sort_keys=True)
a == b # a normal string comparison
This works for nested dictionaries and lists.
回答3:
Decode them and compare them as mgilson comment.
Order does not matter for dictionary as long as the keys, and values matches. (Dictionary has no order in Python)
>>> {'a': 1, 'b': 2} == {'b': 2, 'a': 1}
True
But order is important in list; sorting will solve the problem for the lists.
>>> [1, 2] == [2, 1]
False
>>> [1, 2] == sorted([2, 1])
True
>>> a = '{"errors": [{"error": "invalid", "field": "email"}, {"error": "required", "field": "name"}], "success": false}'
>>> b = '{"errors": [{"error": "required", "field": "name"}, {"error": "invalid", "field": "email"}], "success": false}'
>>> a, b = json.loads(a), json.loads(b)
>>> a['errors'].sort()
>>> b['errors'].sort()
>>> a == b
True
Above example will work for the JSON in the question. For general solution, see Zero Piraeus's answer.
回答4:
For the following two dicts 'dictWithListsInValue' and 'reorderedDictWithReorderedListsInValue' which are simply reordered versions of each other
dictObj = {"foo": "bar", "john": "doe"}
reorderedDictObj = {"john": "doe", "foo": "bar"}
dictObj2 = {"abc": "def"}
dictWithListsInValue = {'A': [{'X': [dictObj2, dictObj]}, {'Y': 2}], 'B': dictObj2}
reorderedDictWithReorderedListsInValue = {'B': dictObj2, 'A': [{'Y': 2}, {'X': [reorderedDictObj, dictObj2]}]}
a = {"L": "M", "N": dictWithListsInValue}
b = {"L": "M", "N": reorderedDictWithReorderedListsInValue}
print(sorted(a.items()) == sorted(b.items())) # gives false
gave me wrong result i.e. false .
So I created my own cutstom ObjectComparator like this:
def my_list_cmp(list1, list2):
if (list1.__len__() != list2.__len__()):
return False
for l in list1:
found = False
for m in list2:
res = my_obj_cmp(l, m)
if (res):
found = True
break
if (not found):
return False
return True
def my_obj_cmp(obj1, obj2):
if isinstance(obj1, list):
if (not isinstance(obj2, list)):
return False
return my_list_cmp(obj1, obj2)
elif (isinstance(obj1, dict)):
if (not isinstance(obj2, dict)):
return False
exp = set(obj2.keys()) == set(obj1.keys())
if (not exp):
# print(obj1.keys(), obj2.keys())
return False
for k in obj1.keys():
val1 = obj1.get(k)
val2 = obj2.get(k)
if isinstance(val1, list):
if (not my_list_cmp(val1, val2)):
return False
elif isinstance(val1, dict):
if (not my_obj_cmp(val1, val2)):
return False
else:
if val2 != val1:
return False
else:
return obj1 == obj2
return True
dictObj = {"foo": "bar", "john": "doe"}
reorderedDictObj = {"john": "doe", "foo": "bar"}
dictObj2 = {"abc": "def"}
dictWithListsInValue = {'A': [{'X': [dictObj2, dictObj]}, {'Y': 2}], 'B': dictObj2}
reorderedDictWithReorderedListsInValue = {'B': dictObj2, 'A': [{'Y': 2}, {'X': [reorderedDictObj, dictObj2]}]}
a = {"L": "M", "N": dictWithListsInValue}
b = {"L": "M", "N": reorderedDictWithReorderedListsInValue}
print(my_obj_cmp(a, b)) # gives true
which gave me the correct expected output!
Logic is pretty simple:
If the objects are of type 'list' then compare each item of the first list with the items of the second list until found , and if the item is not found after going through the second list , then 'found' would be = false. 'found' value is returned
Else if the objects to be compared are of type 'dict' then compare the values present for all the respective keys in both the objects. (Recursive comparison is performed)
Else simply call obj1 == obj2 . It by default works fine for the object of strings and numbers and for those eq() is defined appropriately .
(Note that the algorithm can further be improved by removing the items found in object2, so that the next item of object1 would not compare itself with the items already found in the object2)
回答5:
You can write your own equals function:
- dicts are equal if: 1) all keys are equal, 2) all values are equal
- lists are equal if: all items are equal and in the same order
- primitives are equal if
a == b
Because you're dealing with json, you'll have standard python types: dict, list, etc., so you can do hard type checking if type(obj) == 'dict':, etc.
Rough example (not tested):
def json_equals(jsonA, jsonB):
if type(jsonA) != type(jsonB):
# not equal
return False
if type(jsonA) == dict:
if len(jsonA) != len(jsonB):
return False
for keyA in jsonA:
if keyA not in jsonB or not json_equal(jsonA[keyA], jsonB[keyA]):
return False
elif type(jsonA) == list:
if len(jsonA) != len(jsonB):
return False
for itemA, itemB in zip(jsonA, jsonB):
if not json_equal(itemA, itemB):
return False
else:
return jsonA == jsonB
来源：https://stackoverflow.com/questions/25851183/how-to-compare-two-json-objects-with-the-same-elements-in-a-different-order-equa