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