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python Programming Glossary: default_factoryPython: Change values in dict of nested dicts using items in a list http://stackoverflow.com/questions/11918852/python-change-values-in-dict-of-nested-dicts-using-items-in-a-list import MutableMapping def set_value d keys newkey newvalue default_factory dict Equivalent to `reduce dict.get keys d newkey newvalue`.. for key in keys try val d key except KeyError val d key default_factory else if not isinstance val MutableMapping val d key default_factory.. else if not isinstance val MutableMapping val d key default_factory d val d newkey newvalue Example list_address key1 key1.2 key1.2.1..
Is there a clever way to pass the key to defaultdict's default_factory? http://stackoverflow.com/questions/2912231/is-there-a-clever-way-to-pass-the-key-to-defaultdicts-default-factory there a clever way to pass the key to defaultdict's default_factory A class has a constructor which takes one parameter class C.. defaultdict def __missing__ self key if self.default_factory is None raise KeyError key else ret self key self.default_factory.. is None raise KeyError key else ret self key self.default_factory key return ret d keydefaultdict C d x # returns C x share..
Can I do an ordered, default dict in Python http://stackoverflow.com/questions/6190331/can-i-do-an-ordered-default-dict-in-python class DefaultOrderedDict OrderedDict def __init__ self default_factory None a kw if default_factory is not None and not isinstance.. OrderedDict def __init__ self default_factory None a kw if default_factory is not None and not isinstance default_factory Callable raise.. a kw if default_factory is not None and not isinstance default_factory Callable raise TypeError 'first argument must be callable'..
Parse CSV file and aggregate the values http://stackoverflow.com/questions/8800111/parse-csv-file-and-aggregate-the-values import csv from collections import defaultdict def default_factory return 0 None None 0 reader csv.DictReader open 'test.csv' newline.. open 'test.csv' newline '' cities defaultdict default_factory for row in reader amount int row AMOUNT cities row CITY 0 amount..
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