使用带星号的表达式和变量

Question

我打算删除单词列表中由 "-" 链接的单词。我会使用 starred expression 因为我忽略了我是否会在 split().

列表中获得一个列表

我用常量表达式工作得很好：

[i for i in [*['1','2'],'1']]

产量：

['1', '2', '1']

我将使用变量获得相同的过程：

test=pd.DataFrame( {'columns0' :[['hanging', 'heart', 't-light', 'holder']]})
test.apply(lambda x : [e if len(e.split('-'))==1 else (*e.split('-')) for e in x ])

但如您所料，它不起作用:

  File "<ipython-input-1109-dda6b3df14bb>", line 3
    test.apply(lambda x : [e if len(e.split('-'))==1 else ( *e.split('-')) for e in x ])
                                                           ^
SyntaxError: can't use starred expression here

Answer 1

为什么还要费心区分这些情况？ split returns 列表无论长度如何。只是嵌套理解：

lambda x: [token for e in x for token in e.split('-')]

Answer 2

显然，答案是列表理解不支持拼音。

PEP 总结摘要说："This PEP does not include unpacking operators inside list, set and dictionary comprehensions although this has not been ruled out for future proposals."

来源：https://www.python.org/dev/peps/pep-0448/#id6

在对类似问题的回答中，@Curtis Lustmore 解释说："The assignment operator (and all variations on it) forms a statement in Python, not an expression. Unfortunately, list comprehensions (and other comprehensions, like set, dictionary and generators) only support expressions"

来源：

使用带星号的表达式和变量

Using starred expressions with variables

python

tokenize

nltk