Replace a value in a column by vlookup another dataframe only if the value exists

Question

I want to overwrite my df1.Name values based on a mapping table in (df2.Name1, df2.Name2). However, not all values in df1.Name exist in df2.Name1

df1:

Name
Alex
Maria 
Marias
Pandas
Coala

df2:

Name1   Name2
Alex    Alexs
Marias  Maria
Coala   Coalas

Expected Result:

Name
Alexs
Maria
Maria
Pandas
Coalas

I have tried several solutions online such as using the Map function. By turning df2 in a Dictionary I am using df1.Name = df1.Name.map(Dictionary), but this will result in nan for all values not in df2 as per below.

Name
Alexs
Maria
Maria
NAN
Coalas

I am not sure how to use an IF statement to replace only the ones that do exist in df2 and keep the rest as per df1. I also tried to create a function with if statements, but was big time failure.

How I could approach this problem?

Answer 1

By using replace

df1.Name.replace(df2.set_index('Name1').Name2.to_dict())
Out[437]: 
0     Alexs
1     Maria
2     Maria
3    Pandas
4    Coalas
Name: Name, dtype: object

Answer 2

Let's use a Pandas solution with map and combine_first:

df1['Name'].map(df2.set_index('Name1')['Name2']).combine_first(df1['Name'])

Output:

0     Alexs
1     Maria
2     Maria
3    Pandas
4    Coalas
Name: Name, dtype: object