Python Learning notes 4-python file operations

Python file operations

Open

R: Open in read mode

W: Open in write mode

A: in Append mode

r+: Read/write mode

w+: Read/write mode (see W)

A +: Read-write mode (see a)

RB: Open in binary read mode

WB: Opens in binary write mode (see W)

AB: Open in binary append mode (see a)

rb+: Open in binary read/write mode (see r+)

wb+: Open in binary read/write mode (see w+)

ab+: Open in binary read/write mode (see A +)

With open

Traversing a file with a for loop

Open File

[[email protected] ~]# vim forread.py#!/usr/bin/pythonfd=open ('/tmp/tmp.txt ') for line in FD: #或者使用for line in Fd.readli NES (): ReadLines () creates a list of rows, if the file is 1G, takes up memory large print line, #使用, [[email protected] ~]# python forread.py Daviddavid1david2dav Id3

Traversing a file using a while loop

Open File

[[Email protected] ~]# vim whileread.py #!/usr/bin/pythonfd = open ('/tmp/ Tmp.txt ') while true:    line = fd.readline ()     if  not line:        break    print  Line,fd.close () [[email protected] ~]# python whileread.py daviddavid1david2david3# Use With open ()  AS FD without Fd.close (), with open The following code requires a keyword, which belongs to the looping content [[email protected] ~] # vim whileread.py #!/usr/bin/pythonwith open ('/tmp/tmp.txt ')  as fd:     while true:        line = fd.readline ()         if not line:             break        print line,[[ Email protected] ~]#&nbSp;python whileread.py daviddavid1david2david3 

Print mem Total and mem free, use StartsWith (a) to determine the beginning of a string with a letter A, return true, otherwise return False,split () to split the string

[[email protected] ~]# cat /proc/meminfo memtotal:          502092 kBMemFree:            10656 kbbuffers:          131744 kbcached:            236908 kBSwapCached:            64 kB[[email protected] ~]# vim  memory.py#!/usr/bin/pythonwith open  ('/proc/meminfo ')  as fd:    for  line in fd:        if line.startswith (' MemTotal ') :             total=line.split () [1]         if line.startswith (' Memfree '):             fRee=line.split () [1]print total,free[[email protected] ~]# python memory.py502092  9156

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Python Learning notes 4-python file operations