How to update Pandas DF using a MAP file, but leave the default value if there is no key pair-CodePudding

I have a dataframe and some of the values need to be updated. However, I want to leave the values without a key value as it currently is.

I tried other code but when I run the code it changes all the values without a key pair to NaN.

How do I go from

Df

City       Employer
Toronto    Magna's Automotive
Toronto    Manga
Vancouver  Dunder
Calgary    Flames

mapping file

d = {'Manga':"Magna's Automotive",
     'Dunder': 'Dunder Mifflin',}

Df-desired

City       Employer
Toronto    Magna's Automotive
Toronto    Magna's Automotive
Vancouver  Dunder Mifflin
Calgary    Flames

CodePudding user response：

You can use:

df['Employer'] = df['Employer'].map(d).fillna(df['Employer'])

output:

        City            Employer
0    Toronto  Magna's Automotive
1    Toronto  Magna's Automotive
2  Vancouver      Dunder Mifflin
3    Calgary              Flames

Or, using update for in place modification:

df.update(df['Employer'].map(d))