Reading array from config file in python

Question

I have a problem. My program is using config file to set options, and one of those options is a tuple. Here's what i mean:

[common]
logfile=log.txt
db_host=localhost
db_user=root
db_pass=password
folder[1]=/home/scorpil
folder[2]=/media/sda5/
folder[3]=/media/sdb5/

etc... Can i parse this into tuple with ConfigParser module in Python? Is there some easy way to do this?

Ahab

Answer 1

if you can change config format like this:

folder = /home/scorpil
         /media/sda5/
         /media/sdb5/

then in python:

config.get("common", "folder").split("\n")

Varga

Answer 2

Your config could be:

[common]
logfile=log.txt
db_host=localhost
db_user=root
db_pass=password
folder = ("/home/scorpil", "/media/sda5/", "/media/sdb5/")

Assuming that you have config in a file named foo.cfg, you can do the following:

import ConfigParser
cp = ConfigParser.ConfigParser()
cp.read("foo.cfg")
folder = eval(cp.get("common", "folder"), {}, {})

print folder
print type(folder)

which should produce:

('/home/scorpil', '/media/sda5/', '/media/sdb5/')
<type 'tuple'>

-- EDIT -- I've since changed my mind about this, and would take the position today that using eval in this context is a bad idea. Even with a restricted environment, if the configuration file is under user control it may be a very bad idea. Today I'd probably recommend doing something interesting with split to avoid malicious code execution.

Pelpel

I would agree that in general eval() is not good. In the case where you control the input, and restrict the execution environment it is an acceptable solution. – Pelpel

Evil no, gobsmackingly dangerous yes. The key to safer use of eval() is to ensure that you have specified the global and local parameters to eval(). See docs.python.org/2/library/functions.html#eval for more details. – Pelpel

Answer 3

Create configuration:

folders = ['/home/scorpil', '/media/sda5/', '/media/sdb5/']
config.set('common', 'folders', json.dumps(folders))

Load configuration:

tuple(json.loads(config.get('common', 'folders')))

Scrutiny

Answer 4

You can get the items list and use a list comprehension to create a list of all the items which name starts with a defined prefix, in your case folder

folders = tuple([ item[1] for item in configparser.items() if item[0].startswith("folder")])

Limicoline

This solution assumes that the entries in the file are in the proper order. – Dao

@Terrel Shumway is does but you could always sort the items beforehand. – Limicoline

sorting beforehand won't help: folder[10] < folder[2] – Dao

Answer 5

I don't know ConfigParser, but you can easily read it into a list (perhaps using .append()) and then do myTuple = tuple(myList)

Ovate

Answer 6

#!/usr/bin/env python
sample = """
[common]
logfile=log.txt
db_host=localhost
db_user=root
db_pass=password
folder[1]=/home/scorpil
folder[2]=/media/sda5/
folder[3]=/media/sdb5/
"""
from cStringIO import StringIO
import ConfigParser
import re
FOLDER_MATCH = re.compile(r"folder\[(\d+)\]$").match

def read_list(items,pmatch=FOLDER_MATCH):
    if not hasattr(pmatch,"__call__"):
        pmatch = re.compile(pmatch).match
    folder_list = []
    for k,v in items:
        m = pmatch(k)
        if m:
            folder_list.append((int(m.group(1)),v))
    return tuple( kv[1] for kv in sorted(folder_list) )


if __name__ == '__main__':
    cp = ConfigParser.SafeConfigParser()
    cp.readfp(StringIO(sample),"sample")

    print read_list(cp.items("common"))

Dao

Answer 7

You could stick to json completely

tst.json

{
  "common": {
    "logfile":"log.txt",
    "db_host":"localhost",
    "db_user":"root",
    "db_pass":"password",
    "folder": [
      "/home/scorpil",
      "/media/sda5/",
      "/media/sdb5/"
    ]
  }
}

then work with it

$ python3

>>> import json
>>> with open("tst.json", "r", encoding="utf8") as file_object:
...   job = json.load(file_object)
... 
>>> job
{'common': {'db_pass': 'password', 'logfile': 
'log.txt', 'db_user': 'root', 'folder': 
['/home/scorpil', '/media/sda5/', '/media/sdb5/'], 
'db_host': 'localhost'}}

>>> print (job["common"]["folder"][0])
/home/scorpil
>>> print (job["common"]["folder"][1])
/media/sda5/
print (job["common"]["folder"][2])
/media/sdb5/

>>> folder_tuple = tuple(job["common"]["folder"])
>>> folder_tuple
('/home/scorpil', '/media/sda5/', '/media/sdb5/')

Erickericka