合并来自两个不同数据框的列

Question

I have two different dataframe as shown in the images below. I will like to merge column (C-ORG_PC) in the first dataframe with column (C-ORG_PC) in the second dataframe such that when the SAMPFROM column in both dataframe are equal, It will replace the -99 value at that point in the first dataframe with the corresponding value in the second dataframe.

data1:

SAMPFROM	SAMPTO	C-ORG
0	5	-99
5	10	-99
10	15	-99
15	20	-99
20	25	-99
25	30	-99
30	35	-99
35	40	-99
40	45	-99

data2:

SAMPFROM	SAMPTO	C-ORG
0	20	2.5
20	40	7
40	60	7
60	80	9

 LIST1=list(data1['SAMPFROM'])
LIST2=list(data2['SAMPFROM'])
values=[]
for i in LIST1:
 for j in LIST2:
    if i==j:
        values.append(i)
for k in values:
 for q in data2['SAMPFROM']:
    if k==q:
        data1['new']=data2['CO3_pct_BESTEL']

Answer 1

You can use the code below:

df1 = data1.set_index('SAMPFROM')
df1.update(data2.set_index('SAMPFROM')['C-ORG'])
df1.reset_index()

   SAMPFROM  SAMPTO  C-ORG
0         0       5    2.5
1         5      10  -99.0
2        10      15  -99.0
3        15      20  -99.0
4        20      25    7.0
5        25      30  -99.0
6        30      35  -99.0
7        35      40  -99.0
8        40      45    7.0