[Dynamic Language] Python File Operator

Python File Operator

基本文件操作
In [1]: f = open('test.txt')
In [2]: f.read()
Out[2]: 'abeen....2010-10-21 20:28:10.303459\nabeen....2010-10-21 23:17:51.120509\nabeen....2010-10-21 23:18:13.574263\n'
In [8]: f.readline()
Out[8]: 'abeen....2010-10-21 20:28:10.303459\n'

//读取所有行，返回数组列表
In [17]: l =f.readlines()
In [18]: l
Out[18]:
['abeen....2010-10-21 20:28:10.303459\n',
 'abeen....2010-10-21 23:17:51.120509\n',
 'abeen....2010-10-21 23:18:13.574263\n']

//调整位置
In [16]: f.seek(0)

In [20]: f = open('test.txt', 'w')
In [22]: f.write("this is a test")
In [25]: f.close()
In [26]: f = open('test.txt', 'r')
In [27]: f.read()
Out[27]: 'this is a test'
In [28]: f.close()

//追加内容
In [30]: f = open('test.txt', 'a')
In [31]: f.write("this is append'\n'")
In [32]: f.close()
In [33]: f = open('test.txt', 'r')
In [34]: f.read()
Out[34]: "this is a testthis is append'\n'"

Python在读取一个文件时，会记住其在文件中的位置
In [35]: f.seek(0)
In [36]: f.read(3)
Out[36]: 'thi'
In [37]: f.tell()
Out[37]: 3

有时可能需要以二进制方式读写文件，比如图片和可执行文件。此时，只要在打开文件的方式参数中增加一个“b”即可
In [40]: f = open('test.txt', 'wb')
In [41]: f.write('asdfasdfasd')
In [42]: f.close()
In [46]: f = open('test.txt', 'rb')
In [47]: f.read()
Out[47]: 'asdfasdfasd'
In [48]: f.close()

使用“os.path”来获取基本信息
In [1]: ls
file_test.py  test.txt

In [2]: fils_status = "test.txt"
In [5]: import os
In [6]: print  os.path.isdir(fils_status)
False
In [9]: print  os.path.isfile(fils_status)
True
In [10]: print  os.path.islink(fils_status)
False
In [11]: print  os.path.ismount(fils_status)
False

目录操作

列出目录下内容
In [15]: for filename in os.listdir('file'):
   ....:     print filename
file_test.py
test.txt

创建目录
In [17]: os.mkdir('abeen')
In [18]: ls
abeen/  file_test.py  test.txt
删除目录
In [19]: os.rmdir('abeen')
In [20]: ls
file_test.py  test.txt
多级目录
In [23]: os.makedirs('l/abeen/xiao/sb')
In [24]: ls
file_test.py  l/  test.txt

In [36]: os.removedirs('l/abeen/xiao/sb')
In [37]: ls
file_test.py  test.txt

对指定类型文件进行操作，用fnmatch
In [33]: for file_name in os.listdir('./'):
   ....:     if fnmatch.fnmatch(file_name, '*.txt'):
   ....:         print file_name
test.txt
In [34]: l = ["aa", "aa.txt", "abeen.img", "shanshan.txt"]
In [35]: l
Out[35]: ['aa', 'aa.txt', 'abeen.img', 'shanshan.txt']
In [36]: fnmatch.filter(l,'*.txt')
Out[36]: ['aa.txt', 'shanshan.txt']
In [37]: fnmatch.filter(l,'[a]*')
Out[37]: ['aa', 'aa.txt', 'abeen.img']

创建“虚拟”文件
可以使用“StringIO”模块来创建文件并将其保存在内存中
StringIO

In [39]: import StringIO
In [40]: f = StringIO.StringIO("this is a test")
In [42]: f.read()
Out[42]: 'this is a test'
In [43]: dir(f)
Out[43]:
['__doc__',
 '__init__',
 '__iter__',
 '__module__',
 'buf',
 'buflist',
 'close',
 'closed',
 'flush',
 'getvalue',
 'isatty',
 'len',
 'next',
 'pos',
 'read',
 'readline',
 'readlines',
 'seek',
 'softspace',
 'tell',
 'truncate',
 'write',
 'writelines']
In [45]: f.close()

cStringIO 应该比 StringIO速度快些吧
In [1]: import cStringIO
In [2]: f = cStringIO.StringIO("test by abeen \n test by abeen")
In [3]: f.readline()
Out[3]: 'test by abeen \n'
In [4]: f.readline()
Out[4]: ' test by abeen'
In [5]: f.seek(0)
In [6]: f.read()
Out[6]: 'test by abeen \n test by abeen'
In [7]: dir(f)
Out[7]:
['__class__',
 '__delattr__',
 '__doc__',
 '__format__',
 '__getattribute__',
 '__hash__',
 '__init__',
 '__iter__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 'close',
 'closed',
 'flush',
 'getvalue',
 'isatty',
 'next',
 'read',
 'readline',
 'readlines',
 'reset',
 'seek',
 'tell',
 'truncate']
In [8]: f.close()