This python recursive function flattens a JSON file or a dictionary with nested lists and/or dictionaries. The output is a flattened dictionary that use dot-chained names for keys, based on the dictionary structure. This allows for reconstructing the JSON structure or converting it to other formats without loosing any structural information.

Flatten JSON or a nested dictionary

"""
example: The following JSON document:  
{"maps":[{"id1":"blabla","iscategorical1":"0", "perro":[{"dog1": "1", "dog2": "2"}]},{"id2":"blabla","iscategorical2":"0"}],
"masks":{"id":"valore"},
"om_points":"value",
"parameters":{"id":"valore"}}

will have the following output:
{'masks.id': 'valore', 'maps.iscategorical2': '0', 'om_points': 'value', 'maps.iscategorical1': '0', 
'maps.id1': 'blabla', 'parameters.id': 'valore', 'maps.perro.dog2': '2', 'maps.perro.dog1': '1', 'maps.id2': 'blabla'}
"""

def flattenDict(d, result=None):
    if result is None:
        result = {}
    for key in d:
        value = d[key]
        if isinstance(value, dict):
            value1 = {}
            for keyIn in value:
                value1[".".join([key,keyIn])]=value[keyIn]
            flattenDict(value1, result)
        elif isinstance(value, (list, tuple)):   
            for indexB, element in enumerate(value):
                if isinstance(element, dict):
                    value1 = {}
                    index = 0
                    for keyIn in element:
                        newkey = ".".join([key,keyIn])        
                        value1[".".join([key,keyIn])]=value[indexB][keyIn]
                        index += 1
                    for keyA in value1:
                        flattenDict(value1, result)   
        else:
            result[key]=value
    return result

@higarmi Unfortunately although flattening this dictionary should return 3 book items (book.0.author, book.1.author) it returns the last item.

db = {'store': {'bicycle': {'color': 'red', 'price': 19.95},
  'book': [{'author': 'Nigel Rees',
    'category': 'reference',
    'price': 8.95,
    'title': 'Sayings of the Century'},
   {'author': 'Evelyn Waugh',
    'category': 'fiction',
    'price': 12.99,
    'title': 'Sword of Honour'},
   {'author': 'Herman Melville',
    'category': 'fiction',
    'isbn': '0-553-21311-3',
    'price': 8.99,
    'title': 'Moby Dick'},
   {'author': 'J. R. R. Tolkien',
    'category': 'fiction',
    'isbn': '0-395-19395-8',
    'price': 22.99,
    'title': 'The Lord of the Rings'}]}}

In [15]: flattenDict(db)
Out[15]: 
{'store.bicycle.color': 'red',
 'store.bicycle.price': 19.95,
 'store.book.author': 'J. R. R. Tolkien',
 'store.book.category': 'fiction',
 'store.book.isbn': '0-395-19395-8',
 'store.book.price': 22.99,
 'store.book.title': 'The Lord of the Rings'}

@guneysus Use the below code.

def flattenDict(d,result=None,index=None,Key=None):
    if result is None:
        result = {}
    if isinstance(d, (list, tuple)):
        for indexB, element in enumerate(d):
            if Key is not None:
                newkey = Key
            flattenDict(element,result,index=indexB,Key=newkey)            
    elif isinstance(d, dict):        
        for key in d:
            value = d[key]         
            if Key is not None and index is not None:
                newkey = ".".join([Key,(str(key).replace(" ", "") + str(index))])
            elif Key is not None:
                newkey = ".".join([Key,(str(key).replace(" ", ""))])
            else:
                newkey= str(key).replace(" ", "")
            flattenDict(value,result,index=None,Key=newkey)        
    else:
        result[Key]=d        
    return result

In : flattenDict(db)
Out : 
{
'store.bicycle.color': 'red', 
'store.book.author3': 'J. R. R. Tolkien', 
'store.book.category2': 'fiction', 
'store.book.category3': 'fiction', 
'store.book.category0': 'reference', 
'store.book.category1': 'fiction', 
'store.book.price2': 8.99, 
'store.book.price3': 22.99, 
'store.book.price0': 8.95, 
'store.book.price1': 12.99, 
'store.book.title1': 'Sword of Honour', 
'store.book.title0': 'Sayings of the Century', 
'store.book.author1': 'Evelyn Waugh', 
'store.book.author0': 'Nigel Rees', 
'store.book.author2': 'Herman Melville', 
'store.book.title3': 'The Lord of the Rings', 
'store.bicycle.price': 19.95, 
'store.book.title2': 'Moby Dick', 
'store.book.isbn2': '0-553-21311-3', 
'store.book.isbn3': '0-395-19395-8' }

The code doesn't work for me.The output has many missing keys.
Input File = {
"flow": {
"hosts": {
"name": "Client",
"children": [
{
"name": "www.purizon.co.nz",
"children": [
{
"name": "www.purizon.co.nz"
}
]
},
{
"name": "img.oduvanchiksawa.biz",
"children": [
{
"name": "pon.dedulkasanya.biz"
}
]
},
{
"name": "fpdownload2.macromedia.com"
},
{
"name": "ie9cvlist.ie.microsoft.com"
}
]
},
"size": 180
}
}

Output: {u'flow.size': 180, u'flow.hosts.name': u'Client', u'flow.hosts.children.children.name': u'pon.dedulkasanya.biz', u'flow.hosts.children.name': u'ie9cvlist.ie.microsoft.com'}

Is inverse function available?