Pandas - Create a new column (Branch name) based on another column (City name)

Question

I have the following Python Pandas Dataframe (8 rows):

City Name
     
New York
Long Beach
Jamestown
Chicago
Forrest Park
Berwyn
Las Vegas
Miami

I would like to add a new Column (Branch Name) based on City Name as below:

City Name       Branch Name

New York        New York
Long Beach      New York
Jamestown       New York
Chicago         Chicago
Forrest Park    Chicago
Berwyn          Chicago
Las Vegas       Las Vegas
Miami           Miami 

How do I do that?

Answer 1

You can use .map(). City names not in the dictionnary will be kept.

df["Branch Name"] = df["City Name"].map({"Long Beach":"New York",
                                         "Jamestown":"New York",
                                         "Forrest Park":"Chicago",
                                         "Berwyn":"Chicago",}, na_action='ignore')
df["Branch Name"] = df["Branch Name"].fillna(df["City Name"])