联接两个具有不同键列名称的 DataFrame

问：

我想将 courseFee Dataframe 与 febReg DataFrame 联姻。但它们具有不同的键列名称。对于course，Fee是“CID”，febReg是“course_id”。为什么在此代码中我不能仅使用 left_on= 和 right_on= 参数进行连接？

法典

import pandas as pd

folder = r'C:\Users\pulun\hbrag08\Durga Software\Complete Python Package\Python for Data Science\04. Pandas\DataFrame'
studentDataScr = folder+r'\\student_data.csv'
courseFeeScr = folder+r'\\course_fee.csv'
febRegScr = folder+r'\\february_registration.csv'
janResScr = folder+r'\\january_registration.csv'


def csvReader(fileName, delimiter, *args,):
    x = None
    n = None

    if len(args) == 1:
        for i in args:
            x = i
        n = None
    else:
        x = args
        n = x[0]

    return pd.read_csv(fileName,
                       usecols=x,
                       index_col=n,
                       sep=delimiter)


studentData = csvReader(studentDataScr, ';', 'student_id',
                        'student_name', 'gender', 'mobile_number', 'email')
courseFee = csvReader(courseFeeScr, ';', 'course_id', 'course_name', 'fee')
regColumn = ['student_id', 'course_id']

janReg = csvReader(janResScr, ';', regColumn)
febReg = csvReader(febRegScr, ';', regColumn)

courseFee.rename(columns={'course_id': 'CID'}, inplace=True)

joinTwo = pd.merge(courseFee, febReg, left_on='CID', right_on='course_id')
print(joinTwo.head())

错误输出

Exception has occurred: KeyError
'CID'