Python 中open可以操作文件，在文件操作时 需要找到其中某关键字，然后进行插入 、替换或删除等操作；
所以需要 定位文件指针，seek定位操作位置等；且不需要生成新的附件文件，可操作较大的文件；
1. 指定位置插入数据
def add_host(file_name, host, group):
print file_name, host, group
res= {
'status':True,
'message':''
}
file_name ='./deploy/hosts' if not file_nameelse file_name
try:
i =1
with open(file_name, 'r')as f:
with open(file_name, 'r+')as f_w:
line = f.readline()
while line:
if groupin line:
f_w.seek(f.tell(), 0)
host = host +"\n"
f_w.write(host)
next_line = f.readline()
while next_line:
f_w.write(next_line)
next_line = f.readline()
f_w.truncate()
break
line = f.readline()
i +=1
except IOError:
res['status'] =False
res['message'] ='file wirte false！'
return res
2. 指定位置删除数据
def del_host(file_name, host, group):
res= {
'status':True,
'message':''
}
file_name ='./deploy/hosts' if not file_nameelse file_name
try:
i =1
with open(file_name, 'r')as f:
line = f.readline()
# print f.tell()
while line:
if groupin line:
_this = f.tell()
break
line = f.readline()
i +=1
else:
_this =False
i = i +1
with open(file_name, 'r')as f_r:
lines = f_r.readlines()
f_r.seek(_this, 0)
line = f_r.readline()
while line:
if "[" in line:
_end = f_r.tell()
break
if i ==len(lines):
print i, lines
_end = f_r.tell()
print 'last line', _end
break
line = f_r.readline()
i +=1
else:
_end =False
# print 'start, end', _this, _end
if _this ==False:
res['status'] =False
res['message'] ='start false！'
elif _end ==False:
res['status'] =False
res['message'] ='end false！'
elif _this == _end:
res['status'] =False
res['message'] ='_this == _end！'
else:
print 'start, end', _this, _end
try:
with open(file_name, 'r')as f_r:
with open(file_name, 'r+')as f_w:
f_r.seek(_this, 0)
line = f_r.readline()
host_list = []
while lineand f_r.tell() <= _end:
host ="192.168.100.44" if not hostelse host
print(line, f_r.tell())
host_list.append(f_r.tell())
if line.strip().replace('/n', '') == host:
_host = f_r.tell()
print f_r.tell()
for iin host_list:
if i == _host:
now_location = host_list[host_list.index(i) -1]
print 'now_location', now_location
print 'host it..', line, i
f_w.seek(now_location, 0)
# f_r.readline()
print 'i', i, line
next_line = f_r.readline()
print 'i--', i, next_line
# next_line = line
while next_line:
# print 'next line', next_line
f_w.write(next_line)
next_line = f_r.readline()
# break
f_w.truncate()
line = f_r.readline()
except Exception as e:
res['status'] =False
res['msg'] = e
except Exception as e:
res['status'] =False
res['msg'] = e
return res