best way to read a configuration file

**Paul McGuire** · Jul 18 '05, 08:58 AM

Re: best way to read a configuration file

"Karthikesh Raju" <karthik@james. hut.fi> wrote in message
news:2dy8qimiwq .fsf@itl-pc87.hut.fi...[color=blue]
>
> Hi All,
>
> i am wondering about the best way to read in a configuration file that
> goes like:
>
> ###########
>
> [users]
> source_dir = '/home/karthik/Projects/python'
> data_dir = '/home/karthik/Projects/data'
> result_dir = '/home/karthik/Projects/Results'
> param_file = $result_dir/param_file
> res_file = $result_dir/result_file
> comment = 'this is a comment'
>
> K = 8
> simulate_K = 0
>
> N = 4000
> mod_scheme = 'QPSK'
>
> Na = K+2
>
> ############### #######
>
> As of now i use config parser and i get this in a dictionary but
>
> a) but i have users.na and not users.Na (all the fields are in lower
> case)
>
> b) all the rhs arguements are string, but i have handled this by
> trying " try eval(rhs) ... except ..." block
>
> c) Na = 'K+2' though does not work, would like to have Na = 10, but i
> get users.na = 'K+2'
>
> d) result_file, param_file should actually be should be with pathname
> extensions filled in.
>
> Have looked in c.l.py none one ofthe suggestions was to use
> splitlines, this cant handle blank lines, other was to have config.py
> ..
>
> Hope to get some solution for this ..
>
> with warm regards
>
> karthik
>
>
> --
>
> -----------------------------------------------------------------------
> Karthikesh Raju, email: karthik@james.h ut.fi
> Researcher, http://www.cis.hut.fi/karthik
> Helsinki University of Technology, Tel: +358-9-451 5389
> Laboratory of Comp. & Info. Sc., Fax: +358-9-451 3277
> Department of Computer Sc.,
> P.O Box 5400, FIN 02015 HUT,
> Espoo, FINLAND
> -----------------------------------------------------------------------[/color]

**Paul McGuire** · Jul 18 '05, 08:58 AM

Re: best way to read a configuration file

"Karthikesh Raju" <karthik@james. hut.fi> wrote in message
news:2dy8qimiwq .fsf@itl-pc87.hut.fi...[color=blue]
>
> Hi All,
>
> i am wondering about the best way to read in a configuration file that
> goes like:
>
> ###########
>
> [users]
> source_dir = '/home/karthik/Projects/python'
> data_dir = '/home/karthik/Projects/data'
> result_dir = '/home/karthik/Projects/Results'
> param_file = $result_dir/param_file
> res_file = $result_dir/result_file
> comment = 'this is a comment'
>
> K = 8
> simulate_K = 0
>
> N = 4000
> mod_scheme = 'QPSK'
>
> Na = K+2
>
> ############### #######
>
> As of now i use config parser and i get this in a dictionary but
>
> a) but i have users.na and not users.Na (all the fields are in lower
> case)
>
> b) all the rhs arguements are string, but i have handled this by
> trying " try eval(rhs) ... except ..." block
>
> c) Na = 'K+2' though does not work, would like to have Na = 10, but i
> get users.na = 'K+2'
>
> d) result_file, param_file should actually be should be with pathname
> extensions filled in.
>
> Have looked in c.l.py none one ofthe suggestions was to use
> splitlines, this cant handle blank lines, other was to have config.py
> ..
>
> Hope to get some solution for this ..
>
> with warm regards
>
> karthik
>
>
> --
>
> -----------------------------------------------------------------------
> Karthikesh Raju, email: karthik@james.h ut.fi
> Researcher, http://www.cis.hut.fi/karthik
> Helsinki University of Technology, Tel: +358-9-451 5389
> Laboratory of Comp. & Info. Sc., Fax: +358-9-451 3277
> Department of Computer Sc.,
> P.O Box 5400, FIN 02015 HUT,
> Espoo, FINLAND
> -----------------------------------------------------------------------[/color]

I modified the config parser that is included as an example that ships with
pyparsing, by adding:

iniLines = "\n".join( file("karthik.i ni").readlines( ) )
config = inifile_BNF().p arseString(iniL ines)
pprint.pprint( config.asList() )
for k in config.users.ke ys():
print k,":",config.us ers[k]

This gives the following output:

[['users',
['source_dir ', " '/home/karthik/Projects/python'"],
['data_dir ', " '/home/karthik/Projects/data'"],
['result_dir ', " '/home/karthik/Projects/Results'"],
['param_file ', ' $result_dir/param_file'],
['res_file ', ' $result_dir/result_file'],
['comment ', " 'this is a comment'"],
['K ', ' 8'],
['simulate_K ', ' 0'],
['N ', ' 4000'],
['mod_scheme ', " 'QPSK'"],
['Na ', ' K+2']]]
comment : 'this is a comment'
data_dir : '/home/karthik/Projects/data'
mod_scheme : 'QPSK'
Na : K+2
K : 8
simulate_K : 0
N : 4000
res_file : $result_dir/result_file
result_dir : '/home/karthik/Projects/Results'
source_dir : '/home/karthik/Projects/python'
param_file : $result_dir/param_file

This actually shows the 3 access modes to the results from a pyparsing
parseString() operation:
- as a raw list of tokens (optionally grouped into sublists, giving a parse
tree)
- as an object with attributes (note reference to 'config.users', also
notice that keys are not converted to lower case)
- as a dictionary (access to config.users[k] for each key k)

The 2nd level keys could also be referenced using the form
config.users.da ta_dir, config.users.co mment, etc.

pyparsing also comes with an expression parser and evaluator in its
examples. With some creative merging of the two, I think you could in
fairly short order have a config parser that would handle your Na = K+2 and
res_file = "$result_dir... " config values.

The pyparsing home page is at http://pyparsing.sourceforge.net.

HTH,
-- Paul

**Paul McGuire** · Jul 18 '05, 08:58 AM

Re: best way to read a configuration file

Sorry about that last null post, my fingers tripped over the send button
before I started typing my response.

-- Paul

**Karthikesh Raju** · Jul 18 '05, 08:58 AM

Re: best way to read a configuration file

Thankx paul, will have to download pyparsing, will do in a short will
and try your trick, hope it works well :-)

With warm regards

karthik
--

-----------------------------------------------------------------------
Karthikesh Raju, email: karthik@james.h ut.fi
Researcher, http://www.cis.hut.fi/karthik
Helsinki University of Technology, Tel: +358-9-451 5389
Laboratory of Comp. & Info. Sc., Fax: +358-9-451 3277
Department of Computer Sc.,
P.O Box 5400, FIN 02015 HUT,
Espoo, FINLAND
-----------------------------------------------------------------------

**Kevin Dahlhausen** · Jul 18 '05, 08:59 AM

Re: best way to read a configuration file

I kept this sample from an ealier thread or website. I don't have the
link nor can I give credit to the author. If you have some lattitude
on the exact format of the config file, this may do the trick for you
though:

Python App Macro Lang

class App:
def __init__(self, name):
self._name = name
def name(self):
return self._name

i=123

macrosource = """
print app.name()
i=1
if i==2:
server="interna l.blah.com"
else:
server="externa l.blah.com"

"""

code = compile(macroso urce, '<string>', "exec")
anApp = App('Global App Object')
context = {}

# populate context with fun things
context["app"] = anApp
exec code in context

print "The server is:" + context["server"]
if i != 123:
raise "local variable 'i' changed"

output = """
c:\cygwin\bin\s h -c "python PyAsMacroLang.p y"
Global App Object
The server is:external.bla h.com
"""

best way to read a configuration file

best way to read a configuration file

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