是否有更好的方法在Python中访问深度嵌套的类似JSON的对象？

Question

I often have to deal with accessing deeply nested JSON responses. One way to access an element could be something like this:

json_['foo'][0][1]['bar'][3]

But that's obviously not at all safe. One solution is to use the get method of Python dict and pass {} as the default argument.

json_.get('foo', {})[0][1]['bar'][3]

But that again can raise an IndexError exception which leaves me with a length check for every list element access.

target = json_.get('foo', {})
if not target:
   return
target = target[0]
if len(target) < 2:
   return
target = target[1].get('bar', {})
if len(target) < 4:
   return
target = target[3]   #Finally...

And that's not at all pretty. So, is there a better solution for this?

Answer 1

Just wrap the entire thing in try/except :

try:
    return json_['foo'][0][1]['bar'][3]
except IndexError, KeyError:
    return None

Answer 2

Adding to the other answer, if you want to just ignore the exceptions you could use:

# Wrap this in a function
try:
    return json_['foo'][0][1]['bar'][3]
except (KeyError, IndexError):
    pass

Addtionally, another way is to suppress exceptions is with contextlib.suppress() :

from contextlib import suppress

# Wrap this in a function
with suppress(KeyError, IndexError):
    return json_['foo'][0][1]['bar'][3]