其他声明

if condition:
    body
else:
    body

只有在前面的条件语句全部计算为 False 时，else 语句才会执行它的主体。

if True:
    print "It is true!"
else:
    print "This won't get printed.."

# Output: It is true!

if False:
    print "This won't get printed.."
else:
    print "It is false!"

# Output: It is false!