python--Files and Streams

First, open the file:

Open (name[, mode[, Buffering]): name refers to the file name, mode refers to the modal parameter, and buffering refers to Buffering.

1, if not found will throw an exception.

2. File modes: Mode

' R ': Read mode

' W ': Write mode

' A ': Append mode

' B ': binary mode, such as a sound clip or image, requires the use of binary mode.

' + ': Read/write mode.

3, Buffer: buffering.

Control the buffer of the file, if the parameter is 0 or false,i/o input output is unbuffered (all read and write directly to the hard disk), if 1 or true,i/o is buffered (meaning to use memory instead of hard disk, to make the program faster, Update to hard disk only if flush or close is used).

Numbers greater than 1 represent the size of the buffer (in bytes), 1 or any negative number represents the use of the default buffer size.

Ii. Basic Documentation methods:

1. Read and write:

2. Pipeline output: The function of the Linux shell pipe character, which connects the standard output of a command with the standard input of the next command.

Cat Somefile.txt | Python somescript.py | The sort:somescript.py reads the data from its Sys.stdin (the Cat Somefile.txt writes) and writes the results to its sys.stdout.

3. Random Access:

Seek (offset[, whence]): Moves the current position (where it is read and written) to the location defined by offset and whence. Offset indicates that the offsets must be non-negative. Whence: The default of 0 indicates that the offset is calculated from the beginning of the file. The whence is set to 1 (moves relative to the current position, at which point offset can be a negative number) or 2 (as opposed to the end of the file).

Tell method: Returns the location of the current file.

4. Read-write line: File.readline reads a single line (starting from the current position until a newline character appears, and also reads a newline character)

5. Close the file:

1. You can use the try/finally statement:

Try

#write data to your file

Finally

#file. Close ()

2. Use the WITH statement:

From __future__ import with statement

With open ("Somefile") as Somefile

Do Something (somefile)

6, the basic method of using the file:

7. Iterate over the contents of the file:

1. Use the while loop to process bytes:

2, by line operation:

3. Read all content:

Premise: The file is not very large.

Use read to iterate through each character:

To iterate a row using ReadLines:

4. Use Fileinput to implement lazy iteration:

5. File iterators: File objects are iterative and can be iterated by using them directly in the For loop.

python--Files and Streams