文件操作几个简例

来源：http://www.cnitblog.com/yunshichen/archive/2008/08/11/47900.html

#读写文件 

# ! /usr/bin/python 

#  -*- coding: utf8 -*-  

spath = " D:/download/baa.txt " 

f = open(spath, " w " )  #  Opens file for writing.Creates this file doesn't exist. 

f.write( " First line 1.\n " )

f.writelines( " First line 2. " )

f.close()

f = open(spath, " r " )  #  Opens file for reading 

for  line  in  f:

     print ( " 每一行的数据是:%s " % line)

f.close()

''' 

    知识点: 如何读写文件

''' 

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#遍历文件夹和文件 

import  os

import  os.path

#  os,os.path里包含大多数文件访问的函数,所以要先引入它们. 

#  请按照你的实际情况修改这个路径 

rootdir  =   " d:/download " 

for  parent, dirnames, filenames  in  os.walk(rootdir):

     # case 1: 

     for  dirname  in  dirnames:

         print  ( " parent is: "   +  parent)

         print  ( " dirname is: "   +  dirname)

     # case 2 

     for  filename  in  filenames:

         print  ( " parent is: "   +  parent)

         print  ( " filename with full path : "   +  os.path.join(parent, filename))

''' 知识点:

    * os.walk返回一个三元组.其中dirnames是所有文件夹名字(不包含路径),filenames是所有文件的名字(不包含路径).parent表示父目录.

    * case1 演示了如何遍历所有目录.

    * case2 演示了如何遍历所有文件.

    * os.path.join(dirname,filename) : 将形如"/a/b/c"和"d.java"变成/a/b/c/d.java".

''' 

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#分割路径和文件名 

import  os.path

# 常用函数有三种:分隔路径,找出文件名.找出盘符(windows系统),找出文件的扩展名. 

# 根据你机器的实际情况修改下面参数. 

spath = " D:/download/repository.7z " 

#  case 1: 

p,f = os.path.split(spath);

print ( " dir is: " + p)

print ( " file is: " + f)

#  case 2: 

drv,left = os.path.splitdrive(spath);

print ( " driver is: " + drv)

print ( " left is: " + left)

#  case 3: 

f,ext = os.path.splitext(spath);

print ( " f is: " + f)

print ( " ext is: " + ext)

''' 

    知识点:    这三个函数都返回二元组.

    * case1 分隔目录和文件名

    * case2 分隔盘符和文件名

    * case3 分隔文件和扩展名

''' 

总结:5个函数 

os.walk(spath) 

os.path.split(spath) 

os.path.splitdrive(spath) 

os.path.splitext(spath) 

os.path.join(path1,path2) 

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#复制文件 

import  shutil

import  os

import  os.path

src = " d:\\download\\test\\myfile1.txt " 

dst = " d:\\download\\test\\myfile2.txt " 

dst2 = " d:/download/test/测试文件夹.txt " 

dir1 = os.path.dirname(src)

print ( " dir1 %s " % dir1)

if (os.path.exists(src) == False):

    os.makedirs(dir1)       

f1 = open(src, " w " )

f1.write( " line a\n " )

f1.write( " line b\n " )

f1.close()

shutil.copyfile(src, dst)

shutil.copyfile(src, dst2)

f2 = open(dst, " r " )

for  line  in  f2:

     print (line)

f2.close()

# 测试复制文件夹树 

try :

    srcDir = " d:/download/test " 

    dstDir = " d:/download/test2 " 

     # 如果dstDir已经存在,那么shutil.copytree方法会报错! 

     # 这也意味着你不能直接用d:作为目标路径. 

    shutil.copytree(srcDir, dstDir)

except  Exception as err:

     print  (err)

    

''' 

    知识点:

    * shutil.copyfile:如何复制文件

    * os.path.exists:如何判断文件夹是否存在

    * shutil.copytree:如何复制目录树    

''' 

总结:4个函数 

os.path.dirname(path) 

os.path.exists(path) 

shutil.copyfile(src, dst) 

shutil.copytree(srcDir, dstDir) 

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#实战:文件备份小程序 

import  os

import  shutil

import  datetime

''' 

作用：将目录备份到其他路径。

实际效果：

假设给定目录"/media/data/programmer/project/python" ，

备份路径"/home/diegoyun/backup/“ ，

则会将python目录备份到备份路径下，形如：

/home/diegoyun/backup/yyyymmddHHMMSS/python/xxx/yyy/zzz..

用法:更改这两个参数.

backdir:备份目的地.

copydirs:想要备份的文件夹.

''' 

def  mainLogic():

     # add dirs you want to copy 

    backdir = " d:\\test " 

     print (backdir)

    copydirs = []

    copydirs.append( " d:\\temp " );

     # copydirs.append("d:\\test"); 

    

    

     print ( " Copying files  =================== " )

    start = datetime.datetime.now()

     # gen a data folder for backup 

    backdir = os.path.join(backdir,start.strftime( " %Y-%m-%d " ))

     # print("backdir is:"+backdir) 

    

    kc = 0

     for  d  in  copydirs:

        kc = kc + copyFiles(d,backdir)

    end = datetime.datetime.now()

     print ( " Finished! =================== " )

     print ( " Total files :  "   +  str(kc) )

     print ( " Elapsed time :  "   +  str((end - start).seconds) + "  seconds " )

def  copyFiles(copydir,backdir):

    prefix = getPathPrefix(copydir)

     # print("prefix is:"+prefix )    

    i = 0

     for  dirpath,dirnames,filenames  in  os.walk(copydir):

         for  name  in  filenames:

            oldpath = os.path.join(dirpath,name)

            newpath = omitPrefix(dirpath,prefix)

             print ( " backdir is: " + backdir )           

            newpath = os.path.join(backdir,newpath)

             print ( " newpath is: " + newpath)

             if  os.path.exists(newpath) != True:

                os.makedirs(newpath)  

            newpath = os.path.join(newpath,name)

             print ( " From: " + oldpath + "  to: " + newpath)

            shutil.copyfile(oldpath,newpath)

            i = i + 1 

     return  i    

def  getPathPrefix(fullpath):

     # Giving /media/data/programmer/project/ , get the prefix 

     # /media/data/programmer/ 

    l = fullpath.split(os.path.sep)

     # print(str(l[-1]=="")     

     if  l[ - 1 ] == "" :

        tmp = l[ - 2 ]

     else :

        tmp = l[ - 1 ]

     return  fullpath[0:len(fullpath) - len(tmp) - 1 ]

def  omitPrefix(fullpath,prefix):

     # Giving /media/data/programmer/project/python/tutotial/file/test.py , 

     # and prefix is Giving /media/data/programmer/project/, 

     # return path as python/tutotial/file/test.py 

     return  fullpath[len(prefix) + 1 :]

mainLogic()