[英]Python: slicing a list copy affects the original tuple or list when using nested for loops
我在更改列表或元组的任何列表副本时遇到麻烦。 使用两个嵌套的For循环时,将更改元组,如下所示:
testInput = ( ['foo','foo',], ['foo','foo'] )
testCopy = list(testInput)
for rowIndex, row in enumerate(testCopy):
for columnIndex, column in enumerate(row):
testCopy[rowIndex][columnIndex] = ['bar']
print(testInput)
print(testCopy)
>>>([['bar'], ['bar']], [['bar'], ['bar']])
>>>[[['bar'], ['bar']], [['bar'], ['bar']]]
当仅使用一个for循环时,它按我的预期工作并且仅更改副本:
for rowIndex, row in enumerate(testCopy):
testCopy[rowIndex] = ['bar']
>>>([['foo'], ['foo']], [['foo'], ['foo']])
>>>[['bar'], ['bar']]
无论原始文件是列表还是元组,或者副本是否格式化,都会发生这种情况:
testCopy = testInput
testCopy = list(testInput)
testCopy = testInput[:]
具有递归功能的嵌套列表副本:这样,副本就是与原始副本无关的副本
def copyList(yourList):
yourCopiedList=[]
for listElement in yourList:
if type(listElement)==list:
yourCopiedList.append(copyList(listElement.copy()))
else:
yourCopiedList.append(listElement)
return yourCopiedList
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