File open operation of Python notes

#set( aggregate )
# Collection of unordered elements
# The element is the only , Duplicate elements are automatically filtered

#file Object opening and processing

01 Open file create file object

#open(file, mode=‘r’, buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

fl = open('HelloWorld.txt','w',encoding='utf-8')
fl.write('Hello World')
fl.close()

File open type description ：

• t Text mode ( Default ).
• x Write mode , Create a new file , An error is reported if the file already exists .
• b Binary mode .
• • Open a file to update ( Can read but write ).
• U Universal newline pattern （ Not recommended ）.
• r Open the file read-only . The pointer to the file will be placed at the beginning of the file . This is the default mode .
• rb Open a file in binary format for read-only use . The file pointer will be placed at the beginning of the file . This is the default mode . Generally used for non - text files such as pictures .
• r+ Open a file for reading and writing . The file pointer will be placed at the beginning of the file .
• rb+ Open a file in binary format for reading and writing . The file pointer will be placed at the beginning of the file . Generally used for non - text files such as pictures .
• w Open a file only for writing . Open the file if it already exists , And edit from the beginning , The original content will be deleted . If the file does not exist , Create a new file .
• wb Opening a file in binary format is only used for writing . Open the file if it already exists , And edit from the beginning , The original content will be deleted . If the file does not exist , Create a new file . Generally used for non - text files such as pictures .
• w+ Open a file for reading and writing . Open the file if it already exists , And edit from the beginning , The original content will be deleted . If the file does not exist , Create a new file .
• wb+ Open a file in binary format for reading and writing . Open the file if it already exists , And edit from the beginning , The original content will be deleted . If the file does not exist , Create a new file . Generally used for non - text files such as pictures .
• a Open a file for appending . If the file already exists , The file pointer will be placed at the end of the file . in other words , The new content will be written after the existing content . If the file does not exist , Create a new file to write to .
• ab Open a file in binary format for appending . If the file already exists , The file pointer will be placed at the end of the file . in other words , The new content will be written after the existing content . If the file does not exist , Create a new file to write to .
• a+ Open a file for reading and writing . If the file already exists , The file pointer will be placed at the end of the file . Append mode when the file opens . If the file does not exist , Create a new file for reading and writing .
• ab+ Open a file in binary format for appending . If the file already exists , The file pointer will be placed at the end of the file . If the file does not exist , Create a new file for reading and writing .

02 Read file contents

fl = open('HelloWorld.txt','r',encoding='utf-8')

• file.read([size])
  If not specified, return the whole file , If the file size >2 Double the memory , An empty string is returned when the end of the file is read .
• file.readline()
  Back to the line .
• file.readlines([size])
  Returns a list of the specified number of rows , If not specified, all lines will be returned .

03 Write to the document

• f.write(···)
  If you want to write data other than strings , First convert it to a string .

04 Get current pointer position ( Bytes to file header )

• f.tell()

05 Move the pointer position

• f.seek( Offset ,[ The starting position ])
  The starting position : 0 - The file header , The default value is ; 1 - The current position ; 2 - End of document

06 Close file

• f.close()