合并数据帧中具有相同键值的多行

Question

我有一个看起来像这样的数据结构：

idtenifier    amount    dist_type    new_value    new_value2
1              1.0       normal
1              2.0      new_value
1              1.0      new_value2    
3              1.0       normal    
5              3.0       normal    
5              23.0     new_value2    
2              1.0       normal

我正在寻找这样的结构：

idtenifier    amount    dist_type    new_value    new_value2
1              1.0       normal         2.0          1.0  
3              1.0       normal                      23.0    
5              3.0       normal     
2              1.0       normal

我觉得我尝试执行此操作的方式效率很低，我什至无法在列中分配值

df['new_value'] = np.nan

for idx, row in df.iterrows():
    identifier = row['identifier']
    dist_type = row['dist_type']
    amount = row['amount']
    if idx > 0 and identifier == df.loc[idx-1, 'identifier']:
        print(dist_type)
        if dist_type == 'new_value':
            df.loc[idx-1, 'new_value'] == amount

Answer 1

我们不需要在这里使用for循环，将数据帧一分为二后，对于dist_type不等于normal的情况，我们先做pivot，然后再merge

df1=df.loc[df.dist_type=='normal'].copy()
df2=df.loc[df.dist_type!='normal'].copy()
yourdf=df1.merge(df2.pivot('idtenifier','dist_type','amount').reset_index(),how='left')
yourdf
Out[33]: 
   idtenifier  amount dist_type  new_value  new_value2
0           1     1.0    normal        2.0         1.0
1           3     1.0    normal        NaN         NaN
2           5     3.0    normal        NaN        23.0
3           2     1.0    normal        NaN         NaN