Python 列表理解错误

Question

我想将列表排序为几个月

months = ["Jan", "Feb", "March", "April",
          "May", "June", "July", "Aug",
          "Sept", "Oct", "Nov", "Dec"]

这个函数有效，但我想使用列表理解来代替

def order(values):
    sorted = []
    for month in months:
        if month in values:
            sorted_.append(month)
    return sorted_

order(["April","Jan", "Feb"]

输出 - ['一月'、'二月'、'四月']

我尝试了这个，但出现语法错误，我不知道为什么

sorted_ = [month if month in values for month in months]

Answer 1

在列表推导式中执行条件语句有两种不同的方法，这取决于您是否有 else 子句:

没有 else 子句:

[x for x in y if x == z]
[result for element in list if conditional]

带有 else 子句:

[x if x == z else -x for x in y]
[result if conditional else alternative for element in list] 

注意:这些也可以组合:

[x if x.name == z else None for x in y if x is not None]
[result if conditional2 else alternative for element in list if conditional1]

这相当于:

total_result = []
for x in y:
    if conditional1:
        if conditional2:
            total_result.append(result)
        else:
            total_result.append(alternative)