根据条件从另一个 dataframe 值替换列的值 - Python

Question

My problem is as following:

I have a first dataframe (df1):

Client	Ticket	Region	Profile
BCA	1234	US	Shanon
ERROR	3453	EMEA	Laura
RZ	7988	EUROPE	Mitch
ERROR	2364	US	James
Trp	3429	MX	Roger

This is my second datafrane (df2)

Client	Ticket
HHA	3534
Alphabet	3453
HP	2355
AMD	2364

I would like to replace the 'ERROR' values on the 'Client' column of df1 using the values of df2 'Client' column, but the thing is that I'm having issues to do it based on the 'Ticket' values: In this example, the first ERROR should be replaced by Alphabet based on Ticket 3453 , the second ERROR should be replaced by AMD based on Ticket 2364 .

Finally, the desired output should be something like this:

Client	Ticket	Region	Profile
BCA	1234	US	Shanon
Alphabet	3453	EMEA	Laura
RZ	7988	EUROPE	Mitch
AMD	2364	US	James
Trp	3429	MX	Roger

• Just to mention, the dataframes do not have the same shape

Answer 1

data = df1.merge(df2, on='Ticket', how='left')
data.loc[data.Client_x.eq("ERROR"), "Client_x"] = data.Client_y
data.drop(columns=['Client_y']).rename(columns={'Client_x': 'Client'})

Answer 2

You can assign with map

df1.loc[df1['Client'].eq('ERROR'),'Client'] = df1['Ticket'].map(df2.set_index('Ticket')['Client'])
df1
Out[192]: 
     Client  Ticket  Region Profile
0       BCA    1234      US  Shanon
1  Alphabet    3453    EMEA   Laura
2        RZ    7988  EUROPE   Mitch
3       AMD    2364      US   James
4       Trp    3429      MX     Rog

Answer 3

Here's a way:

df1 = df1.set_index('Ticket')
df1.loc[df1.Client=='ERROR','Client'] = df2.set_index('Ticket').Client
df1.Client = df1.Client.fillna('ERROR')
df1 = df1.reset_index()[['Client', 'Ticket'] + [col for col in df1.columns if col != 'Client']]

Input:

df1
  Client  Ticket  Region Profile
0    BCA    1234      US  Shanon
1  ERROR    3453    EMEA   Laura
2     RZ    7988  EUROPE   Mitch
3  ERROR    2364      US   James
4    Trp    3429      MX   Roger
5  ERROR    9999      US   James

df2
     Client  Ticket
0       HHA    3534
1  Alphabet    3453
2        HP    2355
3       AMD    2364

Output:

     Client  Ticket  Region Profile
0       BCA    1234      US  Shanon
1  Alphabet    3453    EMEA   Laura
2        RZ    7988  EUROPE   Mitch
3       AMD    2364      US   James
4       Trp    3429      MX   Roger
5     ERROR    9999      US   James