代码如下：
#encoding=utf-8
print '中国'
#回退输入文件到起点
#创建一个输入文件，如Socket 允许回到起点，这样就可以读取所有数据
from cStringIO import StringIO
class RewindableFile(object):
def __init__(self, input_file):
self.file = input_file
self.buffer_file = StringIO()
self.at_start = True
try:
self.start = input_file.tell()
except(IOError , AttributeError):
self.start = 0
self._use_buffer = True
def seek(self, offset, whence = 0):
if whence != 0:
raise ValueError('whence = %r; expecting 0' %(whence,))
if offset != self.start:
raise ValueError("offset = %r ; excepting %s" %(offset, self.start))
self.rewind()
def rewind(self):
self.buffer_file.seek(0)
self.at_start = True
def tell(self):
if not self.at_start:
raise TypeError("RewindableFile can't tell ")
return self.start
def _read(self,size):
if size < 0:
y = self.file.read()
if self._use_buffer:
self.buffer_file.write(y)
return self.buffer_file.read() + y
elif size == 0 :
return ""
x = self.buffer_file.read(size)
if(len(x) < size):
y = self.file.read(size - len(x))
if self._use_buffer:
self.buffer_file.write(y)
return x + y
return x
def read(self, size = -1):
x = self._read(size)
if self.at_start and x:
self.at_start = False
self._check_no_buffer()
return x
def readline(self):
s = self.buffer_file.readline()
if s[-1:] == '\n':
return s
t = self.file.readline()
if self._use_buffer:
self.buffer_file.write(t)
self._check_no_buffer()
return s + t
def readlines(self):
return self.read().splitlines(True)
def _check_no_buffer(self):
if not self._use_buffer and self.buffer_file.tell() == len(self.buffer_file.getvalue()):
for n in 'seek tell read readline readlines'.split():
setattr(self, n, getattr(self.file,n,None))
del self.buffer_file
def nobuffer(self):
self._user_buffer = False
file_obj = open(r'd:\123.txt','r')
robj = RewindableFile(file_obj)
for line in robj.readlines():
print line
robj.rewind()
for line in robj.readlines():
print line
file_obj.close()
打印结果如下：
中国
1 a c c 中 国
2 a b c 中 国
1 a c c 中 国
2 a b c 中 国