I am writing a simple file with stats on IP address.
I use this code :
line = str('%s %12g %12g %12g' %(IP, STAT1, STAT2, THSD))
with open(ficresul, 'a+') as fico:
if not any(value == x.rstrip('\r\n') for x in fico):
fico.write(value + '\n' )
fico.close()
and output is something like this:
192.168.0.10 15.8121 15.4317 18
192.168.0.20 18.625 12.5085 18
192.168.0.24 20.8323 23.252 18
192.168.0.17 17.6208 15.9218 18
It work perfectly for a new IP address. But I would like to update the stats if the ip address is already in the file and not write it in a new line.
How can it be done?
The simplest thing is to read the entire file, update it in memory, then write the whole thing back out (if it has changes). Trying to update lines in-place will only work if you don't change the length of any lines, and is probably more error-prone.
When storing the contents in memory, use an OrderedDict to store them by the key you want to do lookups by. OrderedDict will help avoid spurious changes to the ordering of the lines, which might be nice to have. Otherwise you can use a regular dict.
Related
This question already has answers here:
Parse key value pairs in a text file
(7 answers)
Closed 1 year ago.
I'm using a config file to inform my Python script of a few key-values, for use in authenticating the user against a website.
I have three variables: the URL, the user name, and the API token.
I've created a config file with each key on a different line, so:
url:<url string>
auth_user:<user name>
auth_token:<API token>
I want to be able to extract the text after the key words into variables, also stripping any "\n" that exist at the end of the line. Currently I'm doing this, and it works but seems clumsy:
with open(argv[1], mode='r') as config_file:
lines = config_file.readlines()
for line in lines:
url_match = match('jira_url:', line)
if url_match:
jira_url = line[9:].split("\n")[0]
user_match = match('auth_user:', line)
if user_match:
auth_user = line[10:].split("\n")[0]
token_match = match('auth_token', line)
if token_match:
auth_token = line[11:].split("\n")[0]
Can anybody suggest a more elegant solution? Specifically it's the ... = line[10:].split("\n")[0] lines that seem clunky to me.
I'm also slightly confused why I can't reuse my match object within the for loop, and have to create new match objects for each config item.
you could use a .yml file and read values with yaml.load() function:
import yaml
with open('settings.yml') as file:
settings = yaml.load(file, Loader=yaml.FullLoader)
now you can access elements like settings["url"] and so on
If the format is always <tag>:<value> you can easily parse it by splitting the line at the colon and filling up a custom dictionary:
config_file = open(filename,"r")
lines = config_file.readlines()
config_file.close()
settings = dict()
for l in lines:
elements = l[:-1].split(':')
settings[elements[0]] = ':'.join(elements[1:])
So, you get a dictionary that has the tags as keys and the values as values. You can then just refer to these dictionary entries in your pogram.
(e.g.: if you need the auth_token, just call settings["auth_token"]
if you can add 1 line for config file, configparser is good choice
https://docs.python.org/3/library/configparser.html
[1] config file : 1.cfg
[DEFAULT] # configparser's config file need section name
url:<url string>
auth_user:<user name>
auth_token:<API token>
[2] python scripts
import configparser
config = configparser.ConfigParser()
config.read('1.cfg')
print(config.get('DEFAULT','url'))
print(config.get('DEFAULT','auth_user'))
print(config.get('DEFAULT','auth_token'))
[3] output
<url string>
<user name>
<API token>
also configparser's methods is useful
whey you can't guarantee config file is always complete
You have a couple of great answers already, but I wanted to step back and provide some guidance on how you might approach these problems in the future. Getting quick answers sometimes prevents you from understanding how those people knew about the answers in the first place.
When you zoom out, the first thing that strikes me is that your task is to provide config, using a file, to your program. Software has the remarkable property of solve-once, use-anywhere. Config files have been a problem worth solving for at least 40 years, so you can bet your bottom dollar you don't need to solve this yourself. And already-solved means someone has already figured out all the little off-by-one and edge-case dramas like stripping line endings and dealing with expected input. The challenge of course, is knowing what solution already exists. If you haven't spent 40 years peeling back the covers of computers to see how they tick, it's difficult to "just know". So you might have a poke around on Google for "config file format" or something.
That would lead you to one of the most prevalent config file systems on the planet - the INI file. Just as useful now as it was 30 years ago, and as a bonus, looks not too dissimilar to your example config file. Then you might search for "read INI file in Python" or something, and come across configparser and you're basically done.
Or you might see that sometime in the last 30 years, YAML became the more trendy option, and wouldn't you know it, PyYAML will do most of the work for you.
But none of this gets you any better at using Python to extract from text files in general. So zooming in a bit, you want to know how to extract parts of lines in a text file. Again, this problem is an age-old problem, and if you were to learn about this problem (rather than just be handed the solution), you would learn that this is called parsing and often involves tokenisation. If you do some research on, say "parsing a text file in python" for example, you would learn about the general techniques that work regardless of the language, such as looping over lines and splitting each one in turn.
Zooming in one more step closer, you're looking to strip the new line off the end of the string so it doesn't get included in your value. Once again, this ain't a new problem, and with the right keywords you could dig up the well-trodden solutions. This is often called "chomping" or "stripping", and with some careful search terms, you'd find rstrip() and friends, and not have to do awkward things like splitting on the '\n' character.
Your final question is about re-using the match object. This is much harder to research. But again, the "solution" wont necessarily show you where you went wrong. What you need to keep in mind is that the statements in the for loop are sequential. To think them through you should literally execute them in your mind, one after one, and imagine what's happening. Each time you call match, it either returns None or a Match object. You never use the object, except to check for truthiness in the if statement. And next time you call match, you do so with different arguments so you get a new Match object (or None). Therefore, you don't need to keep the object around at all. You can simply do:
if match('jira_url:', line):
jira_url = line[9:].split("\n")[0]
if match('auth_user:', line):
auth_user = line[10:].split("\n")[0]
and so on. Not only that, if the first if triggered then you don't need to bother calling match again - it will certainly not trigger any of other matches for the same line. So you could do:
if match('jira_url:', line):
jira_url = line[9:].rstrip()
elif match('auth_user:', line):
auth_user = line[10:].rstrip()
and so on.
But then you can start to think - why bother doing all these matches on the colon, only to then manually split the string at the colon afterwards? You could just do:
tokens = line.rstrip().split(':')
if token[0] == 'jira_url':
jira_url = token[1]
elif token[0] == 'auth_user':
auth_user = token[1]
If you keep making these improvements (and there's lots more to make!), eventually you'll end up re-writing configparse, but at least you'll have learned why it's often a good idea to use an existing library where practical!
i am quite new to Python and i would like to ask the following:
Let's say for example i have the following .txt file:
USERNAME -- example.name
SERVER -- server01
COMPUTERNAME -- computer01
I would like to search through this document for the 3 keywords: USERNAME, SERVER and COMPUTERNAME and when I find these, I would like to extract their values, a.i "example.name", "server01" and "computer01" respectively for each line.
Is this possible? I have already tried for looking by line numbers, but I would much prefer searching by keywords instead.
Question 2: Somewhere in this .txt file exists a line with the keyword Adresses: which has multiple values but listed in different lines, like such:
Adresses:
6001:8000:1080:142::12
8002:2013:2380:110::53
9007:2013:2380:117::80
.
.
Would there be any way to get all of the listed addresses as a result, not just the first one? The number of said addresses is dynamic, so it may change in the future.
To this i have honestly no idea how to begin. I appreciate any kind of hints or pointing me in the right direction.
Thank you very much for your time and attention!
Like this:
with open("filename.txt") as f:
for x in f:
a = x.split(" -- ")
print(a[1])
If line with given value always starts with keyword you can try something like this
with open('file.txt', 'r') as file:
for line in file:
if line.startswith('keyword'):
keyword, value = line.split(' -- ')
and to gather all the addresses i'd initiate list of addresses beforehand, then add line
addresses.append(value)
inside of if statement
Your best friend for this kind of task will be str.split function. You can put your data in a dict which will map keywords to values :
data = {} # Create a new dict
with open('data.txt') as file: # Open the file containing the data
lines = file.read().split('\n') # Split the file in lines
for line in lines: # For each line
keyword, value = line.split(' -- ') # Extract keyword and value
data[keyword] = value # Put in the dict
Then, you can access your values with data['USERNAME'] for example. This method will work on any document containing a key-value association on each line (even if you have more than 3 keywords). However, it will not work if the same text file contains the addresses in the format you mentionned.
If you want to include the addresses in the same file, you'll need to adapt the code. You can for example check if splitted_line contains two elements (= key-value on the same line, like USERNAME) or only one (= key-value on multiple lines, like Addresses:). Then, you can store in a list all the different addresses, and bound this list to the data dict. It's not a problem to have a dict in the form :
{
'USERNAME': 'example.name',
'Addresses': ['6001:8000:1080:142::12', '8002:2013:2380:110::53']
}
I have a csv file that i need to format first before i can send the data to zabbix, but i enconter a problem in 1 of the csv that i have to use.
This is a example of the part of the file that i have problems:
Some_String_That_ineed_01[ifcontainsCell01removehere],xxxxxxxxx02
Some_String_That_ineed_01vtcrmp01[ifcontainsCell01removehere]-[1],aass
so this is 2 lines from the file, the other lines i already treated.
i need to check if Cell01 is in the line
if 'Cell01' in h: do something.
i need to remove all the content beetwen the [ ] included this [] that contains the Cell01 word and leave only this:
Some_String_That_ineed_01,xxxxxxxxx02
Some_String_That_ineed_01vtcrmp01-[1],aass
else my script already treats quite easy. There must be a better way then what i think which is use h.split in the first [ then split again on the , then remove the content that i wanna then add what is left sums strings. since i cant use replace because i need this data([1]).
later on with the desired result i will add this to zabbix sender as the item and item key_. I already have the hosts,timestamps,values.
You should use a regexp (re module):
import re
s = "Some_String_That_ineed_01[ifcontainsCell01removehere],xxxxxxxxx02"
replaced = re.sub('\[.*Cell01.*\]', '', s)
print (replaced)
will return:
[root#somwhere test]# python replace.py
Some_String_That_ineed_01,xxxxxxxxx02
You can also experiment here.
A shelve that I've created isn't allowing me to access the keys without the following failure.
x = shelve.open('my_shelve.pkl')
x.keys()
bsddb.db.DBPageNotFoundError: (-30986, 'BDB0075 DB_PAGE_NOTFOUND: Requested page not found')
However, I am able to check if the Shelf contains a key like so:
'some-key' in x,
and additionally, the Shelf will return the correct data with
x['some-key']
I don't have the list of keys elsewhere, so I'd like to somehow retrieve the keys so I can retrieve the data, or otherwise fix the issue with the database.
I'm using Python 2.7.6
When the database file is damaged (e.g, maybe by failing to call close on it in the past), you probably can't recover all of its contents (the file format just doesn't have enough redundancy to support that).
However, you could perhaps recover a part of it as follows:
recov = {}
try:
for k in x:
recov[k] = x[k]
except Exception:
pass
It's impossible to predict how many keys (and associated values) you'll be able to recover this way, but at least by not asking for all keys (as I imagine you're doing with x.keys() -- you don't tell us which Python version you're using, but I guess it's 2.something) you might be able to recover some of them...
I have two line in my code which first one is os.unlink and second one is os.symlink. like :
os.unlink(path)
os.symlink(new_path)
The sequence should not be change, The problem is, some times it unlink a file (in other word it remove it's shortcut) but second line could not create symbolic link (do to some addressing issue).
My question is: Is there any all or non transaction tool like the one we have in database, to do both line or non ?
you could try this:
import os
linkname = '/tmp/test.lnk'
orig_target = os.path.realpath(linkname)
os.unlink(linkname)
try:
os.symlink(new_target, linkname)
except:
os.symlink(orig_target, linkname)
maybe check what exceptions can occur and only catch the ones that are relevant.
Strictly speaking it is not possible unless you use Transactional filesystem like TxF (https://en.wikipedia.org/wiki/Transactional_NTFS) because nothing prevents your machine from poweroff between two commands.
I can see 2 ways here:
1) Switch to Database
2) Check all conditions before unlinking. What prevents you from symlinking?