你能阻止 df.append() 的自动字母顺序吗？

Question

我正在尝试将数据附加到日志中，其中列的顺序不是按字母顺序排列但符合逻辑，例如。

Org_Goals_1  Calc_Goals_1  Diff_Goals_1   Org_Goals_2 Calc_Goals_2 Diff_Goals_2

我正在根据不同的变量进行多次计算，并通过在每次运行后附加一个值字典来记录结果。有没有办法阻止 df.append() 函数按字母顺序对列进行排序？

Answer 1

看来您必须在追加操作后对列重新排序：

In [25]:
# assign the appended dfs to merged
merged = df1.append(df2)
# create a list of the columns in the order you desire
cols = list(df1) + list(df2)
# assign directly
merged.columns = cols
# column order is now as desired
merged.columns
Out[25]:
Index(['Org_Goals_1', 'Calc_Goals_1', 'Diff_Goals_1', 'Org_Goals_2', 'Calc_Goals_2', 'Diff_Goals_2'], dtype='object')

示例：

In [26]:

df1 = pd.DataFrame(columns=['Org_Goals_1','Calc_Goals_1','Diff_Goals_1'], data = randn(5,3))
df2 = pd.DataFrame(columns=['Org_Goals_2','Calc_Goals_2','Diff_Goals_2'], data=randn(5,3))
merged = df1.append(df2)
cols = list(df1) + list(df2)
merged.columns = cols
merged
Out[26]:
   Org_Goals_1  Calc_Goals_1  Diff_Goals_1  Org_Goals_2  Calc_Goals_2  \
0     0.028935           NaN     -0.687143          NaN      1.528579   
1     0.943432           NaN     -2.055357          NaN     -0.720132   
2     0.035234           NaN      0.020756          NaN      1.556319   
3     1.447863           NaN      0.847496          NaN     -1.458852   
4     0.132337           NaN     -0.255578          NaN     -0.222660   
0          NaN      0.131085           NaN     0.850022           NaN   
1          NaN     -1.942110           NaN     0.672965           NaN   
2          NaN      0.944052           NaN     1.274509           NaN   
3          NaN     -1.796448           NaN     0.130338           NaN   
4          NaN      0.961545           NaN    -0.741825           NaN   

   Diff_Goals_2  
0           NaN  
1           NaN  
2           NaN  
3           NaN  
4           NaN  
0      0.727619  
1      0.022209  
2     -0.350757  
3      1.116637  
4      1.947526

concat 也会对列进行相同的 alpha 排序，因此看起来您必须在追加后重新排序。

编辑

另一种方法是使用 join:

In [32]:

df1.join(df2)
Out[32]:
   Org_Goals_1  Calc_Goals_1  Diff_Goals_1  Org_Goals_2  Calc_Goals_2  \
0     0.163745      1.608398      0.876040     0.651063      0.371263   
1    -1.762973     -0.471050     -0.206376     1.323191      0.623045   
2     0.166269      1.021835     -0.119982     1.005159     -0.831738   
3    -0.400197      0.567782     -1.581803     0.417112      0.188023   
4    -1.443269     -0.001080      0.804195     0.480510     -0.660761   

   Diff_Goals_2  
0     -2.723280  
1      2.463258  
2      0.147251  
3      2.328377  
4     -0.248114

Answer 2

实际上，我发现 "advanced indexing" 工作得很好

df2=df.ix[:,'order of columns']

Answer 3

如我所见，顺序丢失了，但是在追加时，原始数据应该有正确的顺序。为了保持这一点，假设 Dataframe 'alldata' 和要附加数据的 Dataframe 'newdata'，像 'alldata' 中那样附加和保持列顺序将是：

alldata.append(newdata)[list(alldata)]

（我遇到命名日期字段的问题，其中 'Month' 将在 'Minute' 和 'Second' 之间排序）

你能阻止 df.append() 的自动字母顺序吗？

Can you prevent automatic alphabetical order of df.append()?

pandas

append

alphabetical