因此，我有两个DataFrame：Historic和Applet。历史记录包含我学校过去提供的所有课程的列表，而Applet是我学校目前提供的所有课程的列表

我想合并两个数据框，以便添加我的Applet DataFrame中历史记录中不存在的任何项目，并且所有确实存在的项目都覆盖历史记录中的副本(某些课程可能已更新信息，并应使用该信息。)

我目前正在使用Historic.combine_first(Applet)将两者按其索引合并。但是，我希望重复的条目覆盖其历史条目，而不仅仅是重复条目。

代码：def update2(self):

historic = pd.read_csv('course_history.txt', header=None, sep='"', encoding = 'ISO-8859-1',

names=['Course_ID', 'Course_Title', 'Professor_Name','Meeting_Time','Enrollment','Room','Year','Term','Credit'],index_col=[0,6,7])

winnet = pd.DataFrame(self.data, columns =['Course_ID', 'Course_Title', 'Professor_Name','Meeting_Time','Enrollment','Room','Year','Term','Credit'] )

winnet.set_index(['Course_ID','Year','Term'], inplace=True)

historic3 = historic.combine_first(winnet)

Historic DataFrame：Course_ID Year Term ...

AC 230 01 2020-21 May Accounting Systems Crouse, Justin D. ... ROOM NULL 1.00

AC 429 01 2020-21 May CPA Review Sommermeyer, Eric ... ROOM NULL 1.00

ART 150 01 2020-21 May 20th-Century Art, Media, & Design Fedeler, Barbara J. ... ROOM NULL 1.00

ART 208 01 2020-21 May Photography I Payne, Thomas R. ... ROOM NULL 1.00

PSY 222 01 2018-19 FA Cognitive Psychology Eslick Watkins, A ... ROOM NULL 1.00

Applet DataFrame：Course_ID Year Term

PSY 101 01 2018-19 FA Introduction to Psychology Bane, C T H 9:35AM-11:15AM 40/44/0 LH 330 1.00

PSY 101 02 2018-19 FA Introduction to Psychology Eslick Watkins, A T H 1:00PM-2:40PM 40/43/0 SC 134 1.00

PSY 210 10 2018-19 FA Child Development Munir, S T H 9:35AM-11:15AM 30/10/0 LH 327 0.50

PSY 211 20 2018-19 FA Adolescent Development Munir, S T H 1:00PM-2:40PM 30/6/0 LH 330 0.50

PSY 222 01 2018-19 FA Cognitive Psychology Eslick Watkins, A T H 9:35AM-11:15AM 30/24/0 LH 324 1.00