问题
I'm struggling to figure out as to how I should go about deleting a block of lines from a file. Below is the code
#!/usr/bin/python
import argparse
import re
import string
##getting user inputs
p = argparse.ArgumentParser()
p.add_argument("input", help="input the data in format ip:port:name", nargs='*')
args = p.parse_args()
kkk_list = args.input
def printInFormat(ip, port, name):
formattedText = '''HOST Address:{ip}:PORT:{port}
mode tcp
bind {ip}:{port} name {name}'''.format(ip=ip,
port=port,
name=name)
textWithoutExtraWhitespaces = '\n'.join([line.strip() for line in formattedText.splitlines()])
# you can break above thing
# text = ""
# for line in formattedText.splitlines():
# text += line.strip()
# text += "\n"
return(formattedText)
#####here im writing writing the user inoput to a file and it works great.
#with open("file.txt", "a") as myfile:
# for kkk in kkk_list:
# ip, port, name = re.split(":|,", kkk)
# myfile.write(printInFormat(ip, port, name))
###### here is where im struggling.
for kkk in kkk_list:
ip, port, name = re.split(":|,", kkk)
tobedel = printInFormat(ip, port, name)
f = open("file.txt", "r+")
d = f.readlines()
f.seek(0)
if kkk != "tobedel":
f.write(YY)
f.truncate()
f.close()
As you can see I'm appending the file.txt with user inputs. i.e (format:ip:port:name). File will contain below entries when the script is excuted as ./script.py 192.168.0.10:80:string 192.168.0.10:80:string
Host Address:192.168.0.10:PORT:80
mode tcp
bind 192.168.0.10:80 abc
Host Address:10.1.1.10:PORT:443
mode tcp
bind 10.1.1.10:443 xyz
Now I want to delete the line(s) from file.txt when the user input is given the same way. With the above code being run nothing happens. I'm a beginner and really appreiciate if you help me understand. This question is related to python multiple user args
回答1:
Let me point out the little things you are missing.
for kkk in kkk_list:
ip, port, name = re.split(":|,", kkk)
tobedel = printInFormat(ip, port, name)
f = open("file.txt", "r+")
d = f.readlines()
f.seek(0)
if kkk != "tobedel":
f.write(YY)
f.truncate()
f.close()
You opened the file inside the loop and closing outside. The file object is out of scope. Use
withwhich handles the context automatically for you.It is a bad idea to open a file inside a loop, because it will create so many file descriptor which consumes a lot of resources.
You never mentioned what is
YYwhen you are writing.You can delete lines here as you are trying to delete multiple lines in one go, so
d = f.readlines()should bed = f.read()
Below is the updated the code.
#!/usr/bin/python
import argparse
import re
import string
p = argparse.ArgumentParser()
p.add_argument("input", help="input the data in format ip:port:name", nargs='*')
args = p.parse_args()
kkk_list = args.input # ['192.168.1.10:80:name1', '172.25.16.2:100:name3']
def getStringInFormat(ip, port, name):
formattedText = "HOST Address:{ip}:PORT:{port}\n"\
"mode tcp\n"\
"bind {ip}:{port} name {name}\n\n".format(ip=ip,
port=port,
name=name)
return formattedText
# Writing the content in the file
# with open("file.txt", "a") as myfile:
# for kkk in kkk_list:
# ip, port, name = re.split(":|,", kkk)
# myfile.write(getStringInFormat(ip, port, name))
with open("file.txt", "r+") as f:
fileContent = f.read()
# below two lines delete old content of file
f.seek(0)
f.truncate()
# get the string you want to delete
# and update the content
for kkk in kkk_list:
ip, port, name = re.split(":|,", kkk)
# get the string which needs to be deleted from the file
stringNeedsToBeDeleted = getStringInFormat(ip, port, name)
# remove this from the file content
fileContent = fileContent.replace(stringNeedsToBeDeleted, "")
# delete the old content and write back with updated one
# f.truncate(0)
f.write(fileContent)
# Before running the script file.txt contains
# HOST Address:192.168.1.10:PORT:80
# mode tcp
# bind 192.168.1.10:80 name name1
#
# HOST Address:172.25.16.2:PORT:100
# mode tcp
# bind 172.25.16.2:100 name name3
# After running file.txt will be empty
# as we have deleted both the entries.
回答2:
There are multiple ways do it. I tried to create a new file leaving all the blocks. You can drop the old file and rename the new file as old file. Following is the working code for same.
#!/usr/bin/python
import argparse
import re
import string
##getting user inputs
p = argparse.ArgumentParser()
p.add_argument("input", help="input the data in format ip:port:name", nargs='*')
args = p.parse_args()
kkk_list = args.input # ['192.168.1.10:80:name1', '172.25.16.2:100:name3']
# returns the next block from the available file. Every block contains 3 lines as per definition.
def getNextBlock(lines, blockIndex):
if len(lines) >= ((blockIndex+1)*3):
line = lines[blockIndex*3]
line += lines[blockIndex*3+1]
line += lines[blockIndex*3+2]
else:
line = ''
return line
# file - holds reference to existing file of all blocks. For efficiency keep the entire content in memory (lines variable)
file = open("file.txt", "r")
lines = file.readlines()
linesCount = len(lines)
# newFile holds reference to newly created file and it will have the resultant blocks after filtering
newFile = open("file_temp.txt","w")
# loop through all inputs and create a dictionary of all blocks to delete. This is done to have efficiency while removing the blocks with O(n) time
delDict = {}
for kkk in kkk_list:
ip, port, name = re.split(":|,", kkk)
tobedel = printInFormat(ip, port, name)
delDict[tobedel] = 1
for i in range(linesCount / 3):
block = getNextBlock(lines, i)
if block in delDict:
print 'Deleting ... '+block
else:
#write into new file
newFile.write(block)
file.close()
newFile.close()
#You can drop the old file and rename the new file as old file
Hope it helps!
来源：https://stackoverflow.com/questions/43613658/python-deleting-a-block-of-lines-from-a-file