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 '''

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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()