基于python中键的值的2个字典列表中的2元组列表

Question

我有两个字典lx和ly列表。 lx元素包含感兴趣的键key1 ， ly元素包含key2 。 我想创建一个2元组（a，b）的列表，其中a是lx的字典， b是ly的字典，这样a['key1'] == b['key2'] 。 有没有一种方法可以直接通过列表理解来做到这一点？

我失败的尝试是：

out = [(a,b) for a in lx for b in ly and a['key1'] == b['key2']]

但我收到“分配前引用的局部变量b”错误。

更新：

输入示例为：

lx = [{'key1': 'a', 'xyz': 1}, 
      {'key1': 'b', 'xyz': 2}, 
      {'key1': 'c', 'xyz': 3}]

ly = [{'key2': 'a', 'abc': '66'}, 
      {'key2': 'c', 'abc': '01'}]

输出：

out = [({'key1': 'a', 'xyz': 1}, {'key2': 'a', 'abc': '66'}), 
       ({'key1': 'c', 'xyz': 3}, {'key2': 'c', 'abc': '01'})]

Answer 1

您需要在条件之前使用if来代替and ：

>>> lx = [{'key1': 'foo'},  {'key1': 'foobar'}]
>>> ly = [{'key2': 'foo'},  {'key2': 'bar'}]
>>> [(a,b) for a in lx for b in ly and a['key1'] == b['key2']]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in <listcomp>
UnboundLocalError: local variable 'b' referenced before assignment
>>> [(a,b) for a in lx for b in ly if a['key1'] == b['key2']]
[({'key1': 'foo'}, {'key2': 'foo'})]