Python追加到列表返回无 [英] Python Append to a list returns none

问题描述

我知道已经回答了这个问题的不同版本，例如 [here].1 但我似乎无法让它在我的例子中工作.我正在尝试制作一个名为 ListB 的 ListA 副本，然后向 ListB 添加一个附加项目，即New_Field_Name"，稍后我将其用作数据框的列标题.

I know different versions of this question has been answered for example [here].1 But I just couldn't seem to get it working on my example. I am trying to make a copy of ListA called ListB and then add an additional item to ListB i.e. 'New_Field_Name' in which later on I use as column headers for a dataframe.

这是我的代码:

ListA = ['BUSINESSUNIT_NAME' ,'ISONAME', 'Planning_Channel', 'Planning_Partner', 'Is_Tracked', 'Week', 'Period_Number']
print type(ListA)

输出:

ListB = list(ListA)
print '######', ListB, '#####'

输出:###### ['BUSINESSUNIT_NAME'、'ISONAME'、'Planning_Channel'、'Planning_Partner'、'Is_Tracked'、'Week'、'Period_Number'] #####

Output: ###### ['BUSINESSUNIT_NAME', 'ISONAME', 'Planning_Channel', 'Planning_Partner', 'Is_Tracked', 'Week', 'Period_Number'] #####

ListB = ListB.append('New_Field_Name')
print type(ListB)
print ListB

输出:无

推荐答案

append 不返回任何东西，所以你不能说

append does not return anything, so you cannot say

ListB = ListB.append('New_Field_Name')

它就地修改了列表，所以你只需要说

It modifies the list in place, so you just need to say

ListB.append('New_Field_Name')

或者你可以说

ListB += ['New_Field_Name']

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