在Python中初始化dict的最佳方法是什么? [英] What's the best way to initialize a dict of dicts in Python?

问题描述

在Perl中很多次，我都会做类似的事情:

A lot of times in Perl, I'll do something like this:

$myhash{foo}{bar}{baz} = 1

我如何将其翻译成Python?到目前为止，我有:

How would I translate this to Python? So far I have:

if not 'foo' in myhash:
    myhash['foo'] = {}
if not 'bar' in myhash['foo']:
    myhash['foo']['bar'] = {}
myhash['foo']['bar']['baz'] = 1

有更好的方法吗?

推荐答案

class AutoVivification(dict):
    """Implementation of perl's autovivification feature."""
    def __getitem__(self, item):
        try:
            return dict.__getitem__(self, item)
        except KeyError:
            value = self[item] = type(self)()
            return value

测试:

a = AutoVivification()

a[1][2][3] = 4
a[1][3][3] = 5
a[1][2]['test'] = 6

print a

输出:

{1: {2: {'test': 6, 3: 4}, 3: {3: 5}}}

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