items=[1,2,3,4] def sum(items): head,*tail = items return head+sum(tail) if tail else head
上述代码中的if tail else head如何理解？为何if else 会有这种书写形式？
谢谢
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head+sum(tail) if tail else head is a whole
head+sum(tail) if tail else head
For examplea if a > b else b等价于max(a, b)等价于(a>b)?a:b
a if a > b else b
max(a, b)
(a>b)?a:b
This is syntactic sugar for python, because early python programmers like to use various hacks to implement ? expressions, so python provides this form in syntax
This is a ternary expression in Python
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head+sum(tail) if tail else headis a wholeFor example
a if a > b else b等价于max(a, b)等价于(a>b)?a:bThis is syntactic sugar for python, because early python programmers like to use various hacks to implement ? expressions, so python provides this form in syntax
This is a ternary expression in Python