I'm implementing deep_get
functionality to look inside arbitrarily nested Python 2.7 objects. Primarily for further logging.
This turned out to have surprising amount of quirks. Here's what I ended up with, would appreciate the feedback as I probably missed a few more things.
# coding=utf-8
from __future__ import unicode_literals
import collections
_default_stub = object()
def deep_get(obj, path, default=_default_stub, separator='.'):
"""Gets arbitrarily nested attribute or item value.
Args:
obj: Object to search in.
path (str, hashable, iterable of hashables): Arbitrarily nested path in obj hierarchy.
default: Default value. When provided it is returned if the path doesn't exist.
Otherwise the call raises a LookupError.
separator: String to split path by.
Returns:
Value at path.
Raises:
LookupError: If object at path doesn't exist.
Examples:
>>> deep_get({'a': 1}, 'a')
1
>>> deep_get({'a': 1}, 'b')
LookupError: {'a': 1} has no element at 'b'
>>> deep_get(['a', 'b', 'c'], -1)
'c'
>>> deep_get({'a': [{'b': [1, 2, 3]}, 'some string']}, 'a.0.b')
[1, 2, 3]
>>> class A(object):
>>> def __init__(self):
>>> self.x = self
>>> self.y = {'a': 10}
>>>
>>> deep_get(A(), 'x.x.x.x.x.x.y.a')
10
>>> deep_get({'a.b': {'c': 1}}, 'a.b.c')
LookupError: {'a.b': {'c': 1}} has no element at 'a'
>>> deep_get({'a.b': {'Привет': 1}}, ['a.b', 'Привет'])
1
>>> deep_get({'a.b': {'Привет': 1}}, 'a.b/Привет', separator='/')
1
"""
if isinstance(path, basestring):
attributes = path.split(separator)
elif isinstance(path, collections.Iterable):
attributes = path
else:
attributes = [path]
for i in attributes:
try:
success = False
# 1. access as attr
try:
obj = getattr(obj, i)
success = True
except (AttributeError, TypeError, UnicodeEncodeError):
# 2. access as dict index
try:
obj = obj[i]
success = True
except (TypeError, AttributeError, IndexError, KeyError):
# 3. access as list index
try:
obj = obj[int(i)]
success = True
except (TypeError, AttributeError, IndexError, KeyError,
UnicodeEncodeError, ValueError):
pass
if not success:
msg = "{obj} has no element at '{i}'".format(obj=obj, i=i)
raise LookupError(msg.encode('utf8'))
except Exception:
if _default_stub != default:
return default
raise
return obj
Update: Revised version with history https://gist.github.com/groz/f1838404d48971cc145609c226fdc6a2