python学习——大文件分割与合并

在平常的生活中,我们会遇到下面这样的情况:

你下载了一个比较大型的游戏(假设有10G),现在想跟你的同学一起玩,你需要把这个游戏拷贝给他。

然后现在有一个问题是文件太大(我们不考虑你有移动硬盘什么的情况),假设现在只有一个2G或4G的优盘,该怎么办呢?

有很多方法,例如winrar压缩的时候分成很多小卷,这里不累述。

在学习python之后,我们自己就可以解决这个问题啦。

我们可以自己写一个脚本去分割合并文件,将文件分割成适合优盘大小的小文件,在拷贝,然后再合并。

 

下面是文件分割脚本:

 1 import sys,os
 2 
 3 kilobytes = 1024
 4 megabytes = kilobytes*1000
 5 chunksize = int(200*megabytes)#default chunksize
 6 
 7 def split(fromfile,todir,chunksize=chunksize):
 8     if not os.path.exists(todir):#check whether todir exists or not
 9         os.mkdir(todir)          
10     else:
11         for fname in os.listdir(todir):
12             os.remove(os.path.join(todir,fname))
13     partnum = 0
14     inputfile = open(fromfile,'rb')#open the fromfile
15     while True:
16         chunk = inputfile.read(chunksize)
17         if not chunk:             #check the chunk is empty
18             break
19         partnum += 1
20         filename = os.path.join(todir,('part%04d'%partnum))
21         fileobj = open(filename,'wb')#make partfile
22         fileobj.write(chunk)         #write data into partfile
23         fileobj.close()
24     return partnum
25 if __name__=='__main__':
26         fromfile  = input('File to be split?')
27         todir     = input('Directory to store part files?')
28         chunksize = int(input('Chunksize to be split?'))
29         absfrom,absto = map(os.path.abspath,[fromfile,todir])
30         print('Splitting',absfrom,'to',absto,'by',chunksize)
31         try:
32             parts = split(fromfile,todir,chunksize)
33         except:
34             print('Error during split:')
35             print(sys.exc_info()[0],sys.exc_info()[1])
36         else:
37             print('split finished:',parts,'parts are in',absto)

下面是脚本运行的例子:

我们在F有一个X—MEN1.rar文件,1.26G大小,我们现在把它分割成400000000bit(大约380M)的文件。

Python 3.4.1 (v3.4.1:c0e311e010fc, May 18 2014, 10:45:13) [MSC v.1600 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>> 
File to be split?F:\X-MEN1.rar
Directory to store part files?F:\split
Chunksize to be split?400000000
Splitting F:\X-MEN1.rar to F:\split by 400000000
split finished: 4 parts are in F:\split
>>> 

这是分割后的文件: 

 

下面是文件合并脚本:

 

 1 import sys,os
 2 
 3 def joinfile(fromdir,filename,todir):
 4     if not os.path.exists(todir):
 5         os.mkdir(todir)
 6     if not os.path.exists(fromdir):
 7         print('Wrong directory')
 8     outfile = open(os.path.join(todir,filename),'wb')
 9     files = os.listdir(fromdir) #list all the part files in the directory
10     files.sort()                #sort part files to read in order
11     for file in files:
12         filepath = os.path.join(fromdir,file)
13         infile = open(filepath,'rb')
14         data = infile.read()
15         outfile.write(data)
16         infile.close()
17     outfile.close()
18 if __name__=='__main__':
19         fromdir = input('Directory containing part files?')
20         filename = input('Name of file to be recreated?')
21         todir   = input('Directory to store recreated file?')
22         
23         try:
24             joinfile(fromdir,filename,todir)
25         except:
26             print('Error joining files:')
27             print(sys.exc_info()[0],sys.exc_info()[1])

运行合并脚本,将上面分割脚本分割的文件重组:

Python 3.4.1 (v3.4.1:c0e311e010fc, May 18 2014, 10:45:13) [MSC v.1600 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>> 
Directory containing part files?F:\split
Name of file to be recreated?xman1.rar
Directory to store recreated file?F:\
>>> 

运行之后可以看到F盘下生成了重组的xman.rar

posted on 2014-08-30 22:51  shenghl  阅读(18891)  评论(6编辑  收藏  举报

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