Python - 结合两个字典,连接字符串值？

Question

相关:是否有任何pythonic方法来组合两个dicts(添加两个键中出现的键的值)？

我想合并两个字符串:字符串字典,并连接值.以上帖子建议使用collections.Counter,但它不处理字符串连接.

>>> from collections import Counter
>>> a = Counter({'foo':'bar', 'baz':'bazbaz'})
>>> b = Counter({'foo':'baz'})
>>> a + b
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/collections.py", line 569, in __add__
TypeError: cannot concatenate 'str' and 'int' objects

(我的猜测是Counter尝试设置b['baz']为0.)

我想得到一个结果{'foo':'barbaz', 'baz':'bazbaz'}.连接顺序对我来说无关紧要.什么是干净的Pythonic方法呢？

Answer 1

快译通-理解:

>>> d = {'foo': 'bar', 'baz': 'bazbaz'}
>>> d1 = {'foo': 'baz'}
>>> keys = d.viewkeys() | d1.viewkeys()
>>> {k : d.get(k, '') + d1.get(k, '') for k in keys}
{'foo': 'barbaz', 'baz': 'bazbaz'}

对于Python 2.6及更早版本:

>>> dict((k, d.get(k, '') + d1.get(k, '')) for k in keys)
{'foo': 'barbaz', 'baz': 'bazbaz'}

这适用于任何数量的dicts:

def func(*dicts):
    keys = set().union(*dicts)
    return {k: "".join(dic.get(k, '') for dic in dicts)  for k in keys}
... 
>>> d = {'foo': 'bar', 'baz': 'bazbaz'}
>>> d1 = {'foo': 'baz','spam': 'eggs'}
>>> d2 = {'foo': 'foofoo', 'spam': 'bar'}
>>> func(d, d1, d2)
{'foo': 'barbazfoofoo', 'baz': 'bazbaz', 'spam': 'eggsbar'}