短路評估
Python 最低限度地評估布林表示式。
>>> def true_func():
... print("true_func()")
... return True
...
>>> def false_func():
... print("false_func()")
... return False
...
>>> true_func() or false_func()
true_func()
True
>>> false_func() or true_func()
false_func()
true_func()
True
>>> true_func() and false_func()
true_func()
false_func()
False
>>> false_func() and false_func()
false_func()
False