带有列表理解的python三元迭代

python ternary iteration with list comprehension(带有列表理解的python三元迭代)

问题描述

可以进行三元迭代吗?我的意思的简化版本，虽然这个特定的例子可以用更好的方式完成:

Is ternary iteration possible? A simplistic version of what I mean, though this particular example could be done in a better way:

c = 0  
list1 = [4, 6, 7, 3, 4, 5, 3, 4]  
c += 1 if 4 == i for i in list1 else 0  

一个更实际的例子:

strList = ['Ulis', 'Tolus', 'Utah', 'Ralf', 'Chair']
counter = 0  
counter += 1 if True == i.startswith('U') for i in strList else 0  
return counter  

推荐答案

你的实际例子"写成:

>>> strList = ['Ulis', 'Tolus', 'Utah', 'Ralf', 'Chair']
>>> sum(1 for el in strList if el.startswith('U'))
2

你的另一个例子(如果我理解正确的话)是:

Your other example (if I understand correctly) is:

>>> list1 = [4, 6, 7, 3, 4, 5, 3, 4]
>>> list1.count(4)
3

(或者只是改编 strList 示例，但使用内置方法没有错)

(or just adapt the strList example, but nothing wrong with using builtin methods)

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