"""
Functionality copied
from the toolz package to avoid having
to add toolz
as a dependency.
See
https://github.com/pytoolz/toolz/.
toolz
is released under BSD licence. Below
is the licence text
from toolz
as it appeared when copying the code.
--------------------------------------------------------------
Copyright (c) 2013 Matthew Rocklin
All rights reserved.
Redistribution
and use
in source
and binary forms,
with or without
modification, are permitted provided that the following conditions are met:
a. Redistributions of source code must retain the above copyright notice,
this list of conditions
and the following disclaimer.
b. Redistributions
in binary form must reproduce the above copyright
notice, this list of conditions
and the following disclaimer
in the
documentation
and/
or other materials provided
with the distribution.
c. Neither the name of toolz nor the names of its contributors
may be used to endorse
or promote products derived
from this software
without specific prior written permission.
THIS SOFTWARE
IS PROVIDED BY THE COPYRIGHT HOLDERS
AND CONTRIBUTORS
"AS IS"
AND ANY EXPRESS
OR IMPLIED WARRANTIES, INCLUDING, BUT
NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS
FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.
IN NO EVENT SHALL THE REGENTS
OR CONTRIBUTORS BE LIABLE
FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR
SERVICES; LOSS OF USE, DATA,
OR PROFITS;
OR BUSINESS INTERRUPTION) HOWEVER
CAUSED
AND ON ANY THEORY OF LIABILITY, WHETHER
IN CONTRACT, STRICT
LIABILITY,
OR TORT (INCLUDING NEGLIGENCE
OR OTHERWISE) ARISING
IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN
IF ADVISED OF THE POSSIBILITY OF SUCH
DAMAGE.
"""
import operator
from functools
import reduce
def get_in(keys, coll, default=
None, no_default=
False):
"""
NB: This
is a straight copy of the get_in implementation found
in
the toolz library (
https://github.com/pytoolz/toolz/). It works
with persistent data structures
as well
as the corresponding
datastructures
from the stdlib.
Returns coll[i0][i1]...[iX] where [i0, i1, ..., iX]==keys.
If coll[i0][i1]...[iX] cannot be found, returns ``default``, unless
``no_default``
is specified, then it raises KeyError
or IndexError.
``get_in``
is a generalization of ``operator.getitem``
for nested data
structures such
as dictionaries
and lists.
>>>
from pyrsistent
import freeze
>>> transaction = freeze({
'name':
'Alice',
...
'purchase': {
'items': [
'Apple',
'Orange'],
...
'costs': [0.50, 1.25]},
...
'credit card':
'5555-1234-1234-1234'})
>>> get_in([
'purchase',
'items', 0], transaction)
'Apple'
>>> get_in([
'name'], transaction)
'Alice'
>>> get_in([
'purchase',
'total'], transaction)
>>> get_in([
'purchase',
'items',
'apple'], transaction)
>>> get_in([
'purchase',
'items', 10], transaction)
>>> get_in([
'purchase',
'total'], transaction, 0)
0
>>> get_in([
'y'], {}, no_default=
True)
Traceback (most recent call last):
...
KeyError:
'y'
"""
try:
return reduce(operator.getitem, keys, coll)
except (KeyError, IndexError, TypeError):
if no_default:
raise
return default
