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()