Management of python-files

Input and output of characters
Input (raw_input/input)---> program processing---> Output (print)

I. Three major steps in document management:

1. Open the file; f = open ("filename")
2. Processing of documents;
F.read () can read file contents
F.write ("Hello") cannot write to the file because the default file is opened in R mode;
3. Close and save the file; F.close ()

The file must be closed after it is used because the file object consumes the resources of the operating system.

Two. Summary of several models of the document:

1. R mode:
If the file does not exist, direct error;
The file can only be read and cannot be written;

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2. W Mode:
If the file does not exist, create the file directly;
The file can only be written and cannot be read;
The contents of the original file will be emptied when the file is opened;

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3. r+ Mode:
If the file does not exist, direct error;
Documents can be read or written;
Where the content of the specific write is determined by the file pointer (handle);

Read and write first

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Write first and then read

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4. w+ Mode:
If the file does not exist, create the file directly;
Files can be written and read;
The contents of the original file will be emptied when the file is opened;

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5. A
If the file does not exist, create the file directly;
The file can only be written and cannot be read;
The contents of the write are appended directly to the final file;

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6. A +
If the file does not exist, create the file directly;
Files can be written and read;
The contents of the write are appended directly to the final file;

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7. b
Open the file in binary mode, can be used in combination with r,w,+ and so on;

binary files
To read a binary file, compare slices, videos, etc., open the file with ' RB ' mode
>>> f = open ('/root/test.jpg ', ' RB ')
>>> F.read ()
' \xff\xd8\xff\xe1\x00\x18exif\x00\x00 ' # Hexadecimal representation of bytes



Three. Read the file

Append the contents of the file in the passwd to the Hello.txt

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Read () reads all the contents of the file directly;

ReadLine () reads the file one line at a time, the return type is a string;

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readlines () reads all the contents of the file and returns it as a list;

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xreadlines () Similar generators , the contents of the file are not returned directly in a list;

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Four. Writing the file
Write ("str") # writes a string to a file
Writelines ("[" ["Hello", "World"] ") # writes each element of the sequence to a file;

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Five. Other operations of the file

1.f.seek (offset, option)
The offset, if positive, represents the right offset, or, if negative, the left offset;
option, if 0, the pointer points to the beginning of the file;
If 1, the pointer points to the current position;
If 2, the pointer points to the end of the file;

2.f.flush () Submit a modification to the document;


Six. Several points of note in the documentation:

1. The file object is an iterative data type that can be used for traversing the contents of a file;

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2.with open ("filename") as F: This method avoids the user forgetting to close the file; don't write F.close ()

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Management of python-files