Python 表中列的条件值

我正在尝试这样做：

d={'Month':['January','February','March','April'], 'Saves':[2000, 2100, 1900, 1500]}
saves=pd.DataFrame(data=d)

    Month       Saves
0   January     2000
1   February    2100
2   March       1900
3   April       1500

然后变成这样：

d={'Month':['January','February','March','April'], 'Saves':[2000, 2100, 1900, 1500]}
saves=pd.DataFrame(data=d)

    Month       Saves
0   January     2000
1   February    2100
2   March       1900
3   April       1500

我想创建一个新的列'spend'，其逻辑如下：如果上个月的值大于->是，否则->否，如：

    Month       Saves    Spent
0   January     2000       -
1   February    2100      No
2   March       1900      Yes
3   April       1500      Yes

我不知道该怎么做，尝试了很多方法进行迭代，但都没有成功

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谢谢

您可以使用shift访问下一列

saves['Spent'] = np.where(saves['Saves'] < saves['Saves'].shift(), 'Yes', 'No')


    Month       Saves   Spent
0   January     2000    No
1   February    2100    No
2   March       1900    Yes
3   April       1500    Yes

保存['saved']=np.where（保存['saves']

注意，这里第一行需要区别对待

saves.at[1:,'Spent']=saves.Saves.diff().gt(0).map({True:'No',False:'Yes'}).iloc[1:]
saves
Out[190]: 
      Month  Saves Spent
0   January   2000   NaN
1  February   2100    No
2     March   1900   Yes
3     April   1500   Yes
saves.fillna('')
Out[191]: 
      Month  Saves Spent
0   January   2000      
1  February   2100    No
2     March   1900   Yes
3     April   1500   Yes

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哦，天哪，太谢谢你了，我正要刮我的桌子。很简单，谢谢！如果你想处理第一排，一定要看一下@Wen的答案谢谢你这么快的回答，我已经听了差不多一个小时了！非常感谢你@YelasuHaldYW~你可以考虑接受和赞成你喜欢的答案。