Python:文件操作技巧(File operation)

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
'''

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".
'''

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)

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)

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()