迭代python字典中的一个维度 [英] iterate over a single dimension in python dictionary

问题描述

可能重复:
在python多维关联数组中迭代一个键

Possible Duplicate:
iterating one key in a python multidimensional associative array

我在2维上创建了一个字典 myaddresses ['john'，'smith'] =地址1" myaddresses ['john'，'doe'] =地址2"

i created a dictionary on 2 dimensions myaddresses['john','smith'] = "address 1" myaddresses['john','doe'] = "address 2"

我该如何以一种方式迭代一个维度

How can i iterate over one dimension in the fashion

for key in myaddresses.keys('john'):

推荐答案

坏消息:你不能(至少不是直接).您所做的不是"2维"字典，而是以元组(在您的情况下为字符串对)作为键的字典，并且仅使用键的哈希值(通常与哈希表一起使用).您想要的内容需要顺序查找，即:

Bad news: you can't (not directly at least). What you did was not a "2 dimensions" dict, but a dict with tuples (string pairs in your case) as keys, and only the hash value of the key is used (as usually with hashtables). What you want requires a sequential lookup, ie:

for key, val in my_dict.items():
    # no garantee we have string pair as key here
    try:
        firstname, lastname = key
    except ValueError:
        # not a pair...
        continue
    # this would require another try/except block since
    # equality test on different types can raise anything
    # but let's pretend it's ok :-/
    if firstname == "john":
        do_something_with(key, val)

毋庸置疑，这在使用字典的整个意义上都是失败的.错误...使用适当的关系数据库又如何呢?

Needless to say that it kind of defeat the whole point of using a dict. Err... what about using a proper relational DB instead ?

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