Python - 使用嵌套列表时的奇怪IF语句 [英] Python - Weird IF statement while using nested lists

问题描述

我不明白为什么没有传递 else 条件。有人能解释一下原因吗？

I don't understand why the else condition is not passed. Can somebody explain why?

#Python 3.4    
list=[]
list_of_list=[]

list.append("Test")
list.append("This")
list_of_list.append(list)
list=[]

print(list_of_list)
print(type(list_of_list))
print(len(list_of_list))

for element in list_of_list:
 if(element[0]=="Test"):
     print("[OK]")
 if(element[0]=="NO"):
     print("[OK]Condition is not verified")
 else:
     print("[OK]Why the condition is verified??")#<--------------------------

输出：

[['Test', 'This']]
<class 'list'>
1
[OK]
[OK]Why the condition is verified??

预期输出：

[['Test', 'This']]
<class 'list'>
1
[OK]

如何修复代码？

推荐答案

如果结构，你有两个 ：

You have two if structures here:

if(element[0]=="Test"): # first block
    print("[OK]")
if(element[0]=="NO"): # second block
    print("[OK]Condition is not verified")
else: # attached to second block
    print("[OK]Why the condition is verified??")

element [0] 等于'Test'，它就是这样，所以打印[OK ]。然后检查它是否等于其他东西，当然它不是，所以它然后转到 else 块并打印[OK ]为什么条件被验证？。

element[0] is equal to 'Test', which it is, so it prints "[OK]". It then checks whether it's equal to something else, which of course it isn't, so it then goes to the else block and prints "[OK]Why the condition is verified??".

如果你只想打印一件东西，请使用 elif 将它们连接在一起：

If you want to print only one thing, use elif to connect it all together:

if element[0]=="Test": # first block
    print("[OK]")
elif element[0]=="NO": # attached to first block
    print("[OK]Condition is not verified")
else: # still the same block
    print("[OK]Why the condition is verified??")

这篇关于Python - 使用嵌套列表时的奇怪IF语句的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！