在python中迭代dict dict的dict

Question

I have dict on dict of dict . And I want a function which will return all the details if arguement matches the key like,

identifiers = {
     '42566431313931326462642d3533656132352033': {         
         'name': 'topleft',         
         'subid': {
            'a3e54b84450000': {
                'name': 'north'                
            }
        }        
    },
    '0942378098093': {         
         'name': 'topright',         
         'subid': {
            '4b840000100000000000': {
                'name': 'north'                
            }
        }        
    },
    '4256643131ra98892389': {         
         'name': 'bottomleft',         
         'subid': {
            'a3e54b840000100000000000': {
                'name': 'west'                
            }
        }        
    }
}

def getdetails(p):
    # p could be key of dict or dict of dict
    for key in identifiers:
        if key == p:
            return identifiers[key]        
        else:
            if p in identifiers[key]['subid']:
                return identifiers[key]['subid'][p]

I want to know if there is elegent way to do it (May be using map and lambda)?

Answer 1

Readability is important. As your code is readable, I would improve the code slightly, like this

def getdetails(p):
    if p in ids:
        return ids[p]

    for k, v in ids.iteritems():
        if p in v['subid']:
            return v['subid'][p]

But if you are looking for one-liners, you can create a generator expression and return the first value got from that.

def getdetails(p):
    if p in ids: return ids[p]
    return next(v['subid'][p] for k, v in ids.iteritems() if p in v['subid'])

You can further shorten the code, like this

def getdetails(p):
    return ids.get(p) or next(v['subid'][p] for k, v in ids.iteritems() if p in v['subid'])

The dict.get will return None if the key is not found in the dictionary and that is considered Falsy in Python. So, if it is not in the main dictionary, we will check in the sub dictionaries.

If you are using Python 3.x, you need to use items method instead of iteritems , like this

def getdetails(p):
    return ids.get(p) or next(v['subid'][p] for k, v in ids.items() if p in v['subid'])

Answer 2

for key,value in identifiers.items():
        if key == p:
            return identifiers[key]        
        else:
            if p in identifiers[key]['subid']:
                return identifiers[key]['subid'][p]

Answer 3

If you are sure p to be inside subid if not in top level may be something like below would work as well.

def getdetails(p):
    req_val = identifiers.get(p)
    if not req_val:
       for key, value in identifiers.items():
            req_val = value['subid'].get(p)
    return req_val

Answer 4

Try recursion like this:

def getdetails(p, dictionary):
    result = []
    if type(dictionary) is not dict:
        return result
    for key in dictionary:
        if key == p:
            result.append(dictionary[p])
        result += getdetails(p, dictionary[key])

    return result

print getdetails('name', identifiers)
print getdetails('subid', identifiers)