1. Open the file
Open函数：Open(name[. mode[. buffering]])
The file name is a mandatory parameter, and the mode and buffering are optional parameters.
eg：f = Open(r'C:\text\somefile.txt')
| value | describe |
| r | read mode |
| w | write mode |
| a | Append mode |
| b | Binary mode (processing binary files like sound clips or images) |
| + | read/write mode |
Table 1 Common values of the parameters of the open function mode
| 0 or false | I/O is unbuffered, all read and write operations are directed to the hard disk |
| 1 or true | I/O is buffered, using memory instead of hard disk, making programs faster. Only use flush or close to update the data on the hard disk |
| Greater than 1 | The size of the buffer (in bytes) |
| -1 or how negative | Use default buffer size |
Table 2 open function buffer parameters
2. Read and write
.write() .read()
eg:f = open('somefile.txt','+')
f.write('hello')
f.read()
f.read(4) #4 is the number of characters read
f.close()
3. Tube output
In the UNIX shell, you can use pipes to follow a command to write multiple other commands
eg：$ cat somefile.txt | python somescript.py | sort
cat somefile.txt: write the contents of somefile.txt to standard output (sys.stdout)
python somescript.py: run a python script, the script reads from standard input, and writes the result to standard output
sort: read all text from standard input (sys.stdin), sort alphabetically, and write the result to standard output
The pipe command connects the standard output of one command with the standard input of the next command, so somescript.py reads the data written by somefile.txt from its sys.stdin and writes the result to its sys In .stdout, sort can get data from it.
4. Read and write lines
file.readline reads a single line, including newlines
file.readlines reads all lines of a file and returns them as a list
writelines pass it a list of strings, it will write all the strings to the file without word wrapping
Without writeline, use the write method
5. Close the file
Use the close method
Make sure the file is closed, you can use try/finally, and call close in finally
try:
#write file to your data
finally:
file.close()
You can also use the with statement. The with statement can open a file and assign it to a variable. The file will be automatically closed after the statement ends.
with open("somefile.txt") as somefile:
do_something(somefile)