Add a column in dataframe:

• pd1["NewColumn"] = pd2["ColumnName"]

Replace data in a Pandas dataframe with Python dictionary:

• data = { 'city': ['Tainan', 'Tainan', 'Tainan', 'Taipei', 'Taipei'], 'year': [2015, 2016, 2017, 2015, 2016], 'pop': [1.88, 1.89, 1.89, 2.70, 2.70]}
• df = pd.DataFrame(data)
• print(df)
• city = {'Tainan' : 'TN', 'Taipei' : 'TP'}
• df = df.replace(city)
• print(df)