IF 语句无效语法消息

Question

如何更改 IF 语句？我只得到无效语法

predicted_sentiment = [if score < 0 then 'Negative', if score == 0 then 'Neutral' if score > 0 then 'Positive' for score in sentiment_polarity]

Answer 1

你可能想要：

predicted_sentiment = [
    ('Negative' if score < 0 else 'Neutral' if score == 0 else 'Positive') 
    for score in sentiment_polarity
]

Answer 2

您可以使用 lambda 来提高可读性（有点主观）并简化测试方式（更多 objective）

>>> c = lambda x: 'Negative' if x < 0 else 'Neutral' if x == 0 else 'Positive'
>>> c(2)
'Positive'
>>> c(-2)
'Negative'
>>> c(0)
'Neutral'
>>> sentiment_polarity = [1, 0, -2, 3, -4]
>>> predicted_sentiment = [c(s) for s in sentiment_polarity]
>>> predicted_sentiment
['Positive', 'Neutral', 'Negative', 'Positive', 'Negative']

编辑

你也可以这样使用numpy.sign()

c = lambda x: ['Negative', 'Neutral', 'Positive'][numpy.sign(x)+1]

IF 语句无效语法消息

IF statement invalid syntax message

python

if-statement

编辑