Python：elif还是新的if？

问题描述

最好使用：

if var in X:
    #do_whatever
elif (var in Y):
    #do_whatever2

或：

if var in X:
    #do_whatever
if var in Y:
    #do_whatever2

假设var不能同时出现在X和Y中......是否有任何规则或常规做法？我应该使用elif吗？还是一个新的if？或者没关系??

Assuming var can't be in both X and Y... Is there any rule or common practice? Should I use elif? or a new if? or it doesn't matter??

编辑：很棒的答案..但是，如果第一个语句（#do_whatever）以返回或中断结束，我可以这么说吗？在最后，其他条件将不会被测试因此浪费系统资源或造成麻烦，可以做任何事情......我猜...

Great answers.. But can I say that if the first statement (#do_whatever) ends with a return or a break; where in its end the other condition will not be tested thus wasting the system resources or causing trouble, it's ok to do whatever.. I guess...

推荐答案

在某些情况下会有所不同。
参见此示例：

It makes a difference in some cases.See this example:

def foo(var):
    if var == 5:
        var = 6
    elif var == 6:
        var = 8
    else:
        var = 10

    return var

def bar(var):
    if var == 5:
        var = 6
    if var == 6:
        var = 8
    if var not in (5, 6):
        var = 10

    return var

print foo(5)        # 6
print bar(5)        # 10

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