Python使用自定义合并函数合并字典

问题描述：

我要合并两个字典A和B，以便结果包含：

I want to merge two dictionaries A and B such that the result contains:

所有来自A的对，其中key是唯一的

来自B的所有对，其中键是B的唯一

f（valueA，valueB） li>

All pairs from A where key is unique to A
All pairs from B where key is unique to B
f(valueA, valueB) where the same key exists in both A and B

例如：

def f(x, y):
    return x * y

A = {1:1, 2:3}
B = {7:3, 2:2}

C = merge(A, B)

输出：

{1:1, 7:3, 2:6}

答

感觉像是一个很好的单线程>使用字典视图实现此目的; dict.viewkeys（） result 像一个集合，让你做交叉和对称的差异：

Use dictionary views to achieve this; the dict.viewkeys() result acts like a set and let you do intersections and symmetrical differences:

def merge(A, B, f):
    # Start with symmetric difference; keys either in A or B, but not both
    merged = {k: A.get(k, B.get(k)) for k in A.viewkeys() ^ B.viewkeys()}
    # Update with `f()` applied to the intersection
    merged.update({k: f(A[k], B[k]) for k in A.viewkeys() & B.viewkeys()})
    return merged

在Python 3中，。 viewkeys（）方法已重命名为 .keys（），替换旧的 .keys $ c> function（在Python 2中返回一个列表）。

In Python 3, the .viewkeys() method has been renamed to .keys(), replacing the old .keys() functionality (which in Python 2 returs a list).

上面的 merge（）通用解决方案适用于任何给定的 f（）。

The above merge() method is the generic solution which works for any given f().

演示：

>>> def f(x, y):
...     return x * y
... 
>>> A = {1:1, 2:3}
>>> B = {7:3, 2:2}
>>> merge(A, B, f)
{1: 1, 2: 6, 7: 3}
>>> merge(A, B, lambda a, b: '{} merged with {}'.format(a, b))
{1: 1, 2: '3 merged with 2', 7: 3}

Python使用自定义合并函数合并字典

相关推荐