Python(2.7.x)文件操作的简单示例

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读文件：

定义一个简单的文本处理函数：

def process(text):print "PROCESS:", text

按字节读取：

def process(text):print "PROCESS:", textwith open("tmp.txt") as f:while True:text = f.read(10)if not text:breakprocess(text)

按行读取：

with open("tmp.txt") as f:while True:text = f.readline()if not text:breakprocess(text)

读取所有内容，返回整个字符串文本：

with open("tmp.txt") as f:text = f.read()process(text)f.close()

读取所有内容，返回一个列表，列表的每个元素就是一行内容：

with open("tmp.txt") as f:for line in f.readlines():process(line)

fileinput懒惰行迭代：

当要读取的文件的非常大时，readlines会占有太多的内存，fileinput方法性能更好。

import fileinputfor line in fileinput.input("tmp.txt"):process(line)

文件迭代器（最佳实践）：

with open("tmp.txt") as f:for line in f:process(line)

写文件：

write：

try:with open("tmp.txt", "w") as f:while True:text = raw_input("Please Input: ")if not text:breakf.write(text)except EOFError, e:pass

writelines：

tmp_line = ["hello world", "hi python", "good bye"]with open("tmp.txt", "w") as f:# writelines并不会自动写入换行符f.writelines(tmp_line)

读写综合（文件拷贝示例cp.py）：

from sys import argvfrom sys import exitif len(argv) != 3:exit(1)try:with open(argv[1], "rb") as from_file, open(argv[2], "wb") as to_file:while True:tmp = from_file.read(1024)if not tmp:breakto_file.write(tmp)except IOError as err:print "File Error:", str(err)

序列化：

import cPickle as pwith open("tmp.dat", "w") as f:p.dump(["apple", "mango", "orange"], f)with open("tmp.dat") as f:print p.load(f)

随机访问：

# -*- coding: utf-8 -*- # seek(offset [, whence]) 把当前位置移动到由offset定义的位置。# whence的值为0时（默认），表示相对位置是文件开头处；# whence的值为1时，表示相对位置是当前位置；# whence的值为2时，表示相对位置是文件结尾处。# tell方法返回当前文件的位置。with open("tmp.txt") as f:print f.read(10)print "pos:", f.tell()f.seek(0)print "pos:", f.tell()print f.read()print "pos:", f.tell()

os.path模块:

遍历目录：

# -*- coding: utf-8 -*- import sysimport osdef formate_filename(filename, deep = 0):tab = ''d = 0while d < deep:tab += '  'd += 1return tab + os.path.basename(filename)def list_dir(dirname, deep = 0):if not os.path.exists(dirname):print dirname, 'is not existed'sys.exit(1)if os.path.isfile(dirname):print formate_filename(dirname, deep)if os.path.isdir(dirname):print formate_filename(dirname, deep) + ":"# 列出目录的所有文件和子目录filenames = os.listdir(dirname)for filename in filenames:list_dir(dirname + os.sep + filename, deep + 1)if len(sys.argv) < 2:sys.exit(1)del sys.argv[0]for dirname in sys.argv:list_dir(dirname)print

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