括号对Python中的'或'运算符有什么影响？

Question

python中这两个语句之间有区别吗:

if tag == ('/event' or '/organization' or '/business'):

和

if tag == '/event' or '/organization' or '/business':

Answer 1

他们都错了.你需要的是:

if tag == '/event' or tag == '/organization' or tag == '/business':

要么:

if tag in ['/event', '/organization', '/business']:

Answer 2

适当的解决方案是

if tag in ('/event', '/organization', '/business'):

它不仅使用in完美的操作符,而且还使用元组(不可变),因此python解释器可以比(可变)列表更好地优化它.

基准显示元组比列表更快:

In [1]: import timeit
In [2]: t1 = timeit.Timer('"b" in ("a", "b", "c")')
In [3]: t2 = timeit.Timer('"b" in ["a", "b", "c"]')

In [4]: t1.timeit(number=10000000)
Out[4]: 0.7639172077178955

In [5]: t2.timeit(number=10000000)
Out[5]: 2.240161895751953