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• "r": Opens file in read mode.


• "w": Opens file in write mode. If a file already exists when file is opened, the previous file's contents will be deleted.


• "a": Opens file in write mode. Output will always be appended to the end of the file.

Using "+" opens the file in read-write mode (RDWR):

• 
  
  "r+": Sets the read-write position to the beginning of the file.


• "w+": The same as "r+", but if a file already exists when file is opened, the previous file's contents will be deleted.


• "a+": The same as "r+", but if a file already exists when file is opened, the read-write position will be set to the end of the file.

The "b" flag can also be added to any of these (in the format "r+b") to open the file in binary mode.

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대충 r은 읽기모드. w는 쓰기모드라는 건 알겠는데..

Q1.  w와 a의 차이점.

Q2. +의 기능은?  안 붙이면 파일의 첫단부터 읽는거고 붙이면 마지막단부터읽는게 맞는지...

Q3. b는 ? 제한모드라는데 전혀 감을 못잡겠네요.