为什么行得通? [英] Why does it work?
问题描述
因此，我正在学习Python并研究一系列程序思想.当然，我写了强制性的FizzBuzz，它起作用了，但是基本上是其他语言.我用谷歌搜索它是否还有其他方法，并发现了这种潮湿的单线:
So I'm learning Python and working through a list of program ideas. Of course I wrote the obligatory FizzBuzz, which worked, but was basically if elif else blablabla. I googled it to see if there are other ways and found this dank one-liner:
for i in range(1,101):
print("Fizz" * (i % 3 == 0) + "Buzz" * (i % 5 == 0) or i)
没有ifs，没有elifs，什么也没有.我用Google搜索了字符串连接"，并找到了*符号的信息，但在这种情况下不了解它的工作方式.有人可以解释吗?
There are no ifs, no elifs, nothing. I googled "string concatenation" and found info on the * symbol, but don't understand how it's working in this case. Can somebody explain?
推荐答案
没有ifs，没有elifs，什么也没有.
There are no ifs, no elifs, nothing.
当然有！只是变相.查找字符串连接(即+)对您没有帮助，因为*是重复.具体来说，字符串* n为您提供一个字符串，该字符串是一行中n个字符串的副本.此外，布尔值可以隐式转换为整数:True变为1，而False变为0.所以
Sure there are! Just disguised. Looking for string concatenation (i.e. +) won't help you, because * is repetition. Specifically, string * n gives you a string that is n copies of string in a row. Further, a boolean value can be implicitly converted to an integer: True becomes 1 and False becomes 0. So
"Fizz" * (i % 3 == 0)
表示如果i % 3 == 0，则为一个Fizz，否则为否."与Buzz相同.
means "One Fizz if i % 3 == 0, none if not." Same with Buzz.
最后，末尾的or i表示如果由于两个部分都为空而得到空字符串，则改为得到i. or的真正含义是除非左侧为假值，否则左侧的值，在这种情况下，将返回右侧的值."
Finally, that or i at the end means that if you got the empty string because both parts came up empty, then you get i instead. or really means "the value of the left hand side unless the left hand side is a false value, in which case return the value of the right hand side."
此技巧也在其他地方使用. Python没有直接等同于C的?:运算符，但是由于上面提到的布尔到整数转换，您可以使用两个元素的元组和一个索引操作来接近它.所以C的
This trick gets used elsewhere, too. Python doesn't have a direct equivalent to C's ?: operator, but you can get close to one with a two-element tuple and an index operation because of the bool-to-integer conversion I mentioned above. So C's
a? b: c
表示"b，如果a为true，否则为c"在Python中变为:
which means "b if a is true, otherwise c" becomes this in Python:
(c, b)[a]
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