如何将每个字典值插入到对应键之后的列表中？

Question

我有一个元素列表，我想在关键元素之后将字典值插入到该列表中：

listicle = ['a', 'b', 'c', 'd']
some_new_elements = {'b':'x', 'd':'y'}

给出以下内容：

['a', 'b', 'x', 'c', 'd', 'y']

Pythonic 的方法是什么？

Answer 1

尝试使用itertools.chain.from_iterable这就像一个flatmap ：

from itertools import chain
listicle = ['a', 'b', 'c', 'd']
some_new_elements = {'b':'x', 'd':'y'}
output = list(chain.from_iterable([[x, some_new_elements[x]] if x in some_new_elements else [x] for x in listicle]))
print(output) # output:  ['a', 'b', 'x', 'c', 'd', 'y']

Answer 2

正确的方法：

import itertools

listicle = ['a', 'b', 'c', 'd']
some_new_elements = {'b':'x', 'd':'y'}

new_map = ([m, some_new_elements[m]] if m in some_new_elements else [m] for m in listicle)
print(list(itertools.chain.from_iterable(new_map)))
>>> ['a', 'b', 'x', 'c', 'd', 'y']

一种无需列表理解的简单方法：

listicle = ['a', 'b', 'c', 'd']
some_new_elements = {'b':'x', 'd':'y'}

output = []
for x in listicle:
    output.append(x)
    if(x in some_new_elements):
        output.append(some_new_elements[x])

print(output)
>>>['a', 'b', 'x', 'c', 'd', 'y']

Answer 3

这是执行此操作的理解：

>>> listicle = ['a', 'b', 'c', 'd']
>>> some_new_elements = {'b':'x', 'd':'y'}
>>> sentinel=object()
>>> [x for t in ((e, some_new_elements.get(e, sentinel)) for e in listicle) for x in t if x !=sentinel]
['a', 'b', 'x', 'c', 'd', 'y']