2010年1月13日 · Besides hashtables, another common way to implement dictionaries is red-black trees. Each method has its own pros and cons. A red-black tree can always perform a lookup in O(log N). A hashtable can perform a lookup in O(1) time although that can degrade to O(N) depending on the input.

Section 6.6 of The C Programming Language presents a simple dictionary (hashtable) data structure. I don't think a useful dictionary implementation could get any simpler than this.

2015年9月28日 · I have two dictionaries, and I need to find the difference between the two, which should give me both a key and a value. I have searched and found some addons/packages like datadiff and dictdiff-master, but when I try to import them in Python 2.7, it says that no such modules are defined. I used a set here:

Here are quite a few ways to add dictionaries. You can use Python3's dictionary unpacking feature: ndic = {**dic0, **dic1} Note that in the case of duplicates, values from later arguments are used. This is also the case for the other examples listed here.

I am trying to implement a dictionary (as in the physical book). I have a list of words and their meanings. What data structure / type does Java provide to store a list of words and their meanin

2010年7月21日 · It's not that key is a special word, but that dictionaries implement the iterator protocol. You could do this in your class, e.g. see this question for how to build class iterators. In the case of dictionaries, it's implemented at the C level. The details are available in PEP 234. In particular, the section titled "Dictionary Iterators":

2021年11月17日 · If the value comes from the user, then care needs to be taken to use Object.hasOwnProperty.call(dictionary, key) (otherwise the user can enter a value of valueOf and dictionary['valueOf'] returns the Object.valueOf() function belonging to the Object prototype which is probably not what your code would expect - potential bug or security issue).

Assuming two dictionaries of dictionaries, one might recursively merge them in a single function, but you should be careful not to modify the dictionaries from either source, and the surest way to avoid that is to make a copy when assigning values. As keys must be hashable and are usually therefore immutable, it is pointless to copy them:

I have two existing dictionaries, and I wish to 'append' one of them to the other. By that I mean that the key,values of the other dictionary should be made into the first dictionary. For example: ...

2012年3月22日 · NB: If one wants to lazily maintain a Union "view" of two or more dictionaries, check collections.ChainMap in the standard library - as it has all dictionary methods and cover corner cases not contemplated in the example above.