Edit configuration file through python

Question

I need to edit a configuration file through python and i tried searching on stackoverflow and google and they don't cover my situation, since i need to replace lines in the file and perform matches in my search.

Also, what i found covers how to do it for one line, i will be performing at least 8 line replacements in the file and I would like to know if there is a cleaner and more elegant way of doing this than putting 10 replace(foo, bar) lines altogether.

I need to "match" lines like "ENABLEPRINTER", "PRINTERLIST", "PRNT1.PORT". I want to match thesse text and ignore whatever follows (ex: "=PRNT1, PRNT2").

So i would do something like

replace('ENABLEPRINTER', 'y')
replace('PRINTERLIST', 'PRNT3) 

The file looks like this:

ENABLEPRINTER=n
PRINTERLIST=PRNT1, PRNT2

PRNT1.PORT=9600
PRNT1.BITS=8

Also note these files are about 100 lines and i need to edit about 10 of them.

Thank you very much for your help.

UPDATE:

Using the code posted by @J.F. Sebastian, i'm now getting the following error:

configobj.ParseError: Parse error in value at line 611.

Line 611 of the file is:

log4j.appender.dailyRollingFile.DatePattern='.'yyyy-MM-d

So the problem is with the ' character.

If I comment out that line, the script is working fine with the code posted by @J.F. Sebastian.

Answer 1

import re 
pat = re.compile('ENABLEPRINTER|PRINTERLIST|PRNT1.PORT')

def jojo(mat,dic = {'ENABLEPRINTER':'y',
                    'PRINTERLIST':'PRNT3',
                    'PRNT1.PORT':'734'} ):
    return dic[mat.group()]

with open('configfile','rb+') as f:
    content = f.read()
    f.seek(0,0)
    f.write(pat.sub(jojo,content))
    f.truncate()

Before:

ENABLEPRINTER=n 
PRINTERLIST=PRNT1, PRNT2  

PRNT1.PORT=9600 
PRNT1.BITS=8

After:

y=n 
PRNT3==PRNT1, PRNT2  

734=9600
PRNT1.BITS=8

Too simple to be definitive. Say what are the errors or weaknesses.

The advantage of regexes is they can be modulated easily to particular cases.

.

EDIT:

I've just seen that:

"what i want to do is assign a new value to the variable "

you could inform of that earlier !

Could you give an exemple of file before / after , please.

.

EDIT 2

Here's the code to change the values of certain variables in a file:

import re
from os import fsync

def updating(filename,dico):

    RE = '(('+'|'.join(dico.keys())+')\s*=)[^\r\n]*?(\r?\n|\r)'
    pat = re.compile(RE)

    def jojo(mat,dic = dico ):
        return dic[mat.group(2)].join(mat.group(1,3))

    with open(filename,'rb') as f:
        content = f.read() 

    with open(filename,'wb') as f:
        f.write(pat.sub(jojo,content))



#-----------------------------------------------------------

vars = ['ENABLEPRINTER','PRINTERLIST','PRNT1.PORT']
new_values = ['y','PRNT3','8310']
what_to_change = dict(zip(vars,new_values))


updating('configfile_1.txt',what_to_change)

Before:

ENABLEPRINTER=n 
PRINTERLIST=PRNT1, PRNT2  

PRNT1.PORT=9600 
PRNT1.BITS=8

After:

ENABLEPRINTER=y 
PRINTERLIST=PRNT3

PRNT1.PORT=8310 
PRNT1.BITS=8

Answer 2

If the file is in java.util.Properties format then you could use pyjavaproperties:

from pyjavaproperties import Properties

p = Properties()
p.load(open('input.properties'))

for name, value in [('ENABLEPRINTER', 'y'), ('PRINTERLIST', 'PRNT3')]:
    p[name] = value
p.store(open('output.properties', 'w'))

It is not very robust, but various fixes for it could benefit people who come next.

---

To replace multiple times in a short string:

for old, new in [('ENABLEPRINTER', 'y'), ('PRINTERLIST', 'PRNT3')]:
    some_string = some_string.replace(old, new)

To replace variables names in a configuration file (using configobj module):

import configobj

conf = configobj.ConfigObj('test.conf')

for old, new in [('ENABLEPRINTER', 'y'), ('PRINTERLIST', 'PRNT3')]:
    conf[new] = conf[old]
    del conf[old]
conf.write()

If by replace('ENABLEPRINTER', 'y') you mean assign y to the ENABLEPRINTER variable then:

import configobj

ENCODING='utf-8'
conf = configobj.ConfigObj('test.conf', raise_errors=True,
    file_error=True,           # don't create file if it doesn't exist
    encoding=ENCODING,         # used to read/write file
    default_encoding=ENCODING) # str -> unicode internally (useful on Python2.x)

conf.update(dict(ENABLEPRINTER='y', PRINTERLIST='PRNT3'))
conf.write()

---

It seems configobj is not compatible with:

name = '.'something

You could quote it:

name = "'.'something"

Or:

name = '.something'

Or

name = .something

---

conf.update() does something similar to:

for name, value in [('ENABLEPRINTER', 'y'), ('PRINTERLIST', 'PRNT3')]:
    conf[name] = value