[Tutor] search function (original) (raw)

Kent Johnson kent_johnson at skillsoft.com
Fri Jul 30 15:17:21 CEST 2004

Conrad,

Regular expressions are your friends if you get to know them! You can do what you want with just one RE using subgroup matches. I don't know if it's more Pythonic, but it's more concise and a better use of REs. A more Pythonic way to iterate the config file is to use "for line in config_file".

Say you want to search for two variables, v1 and v2. Then you can use this RE: r'"(v1|v2)"="([^"]*?)"$'

The first group (v1|v2) will match the actual variable name and the second group ([^"]*?) will match the value. The quotes are outside the parentheses so they won't be included in the groups.

(BTW I think this will work just as well: r'"(v1|v2)"="([^"]*)"' - I left in the ? and $ as they were in your original post)

You could also allow for white space around the = by adding \s* on each side of it: r'"(v1|v2)"\s*=\s*"([^"]*)"' .

One final note: If your input string with the variable names could have spaces after the commas, you might want to use re.split() to split it, or if you have control over the calling function maybe pass it as a list of names or a space-delimited string. Or use a combination of split, strip and join like this: altVars = '|'.join([s.strip() for s in variables.split(',')])

Below is a complete program with the re-written function and a simple test harness.

Kent

#####################################

import re

def display_var(config_file, variables): altVars = variables.replace(',','|') var_disp = re.compile(r'"(%s)"="([^"]*?)"$' % altVars)

 for line in config_file:
     match = var_disp.search(line)
     if match:
         print "%s: %s" % match.group(1, 2)

testData = ''' "var3"="33" "var1"="value1" "var2"="22" "dontcare"="42" '''

vars = 'var1,var2,var3'

import StringIO config = StringIO.StringIO(testData)

display_var(config, vars)

At 10:55 AM 7/29/2004 -0700, Conrad wrote:

I'm writing a script that extracts values from config files in the form of:

"variable"="value" "variable1"="value" I wrote this function, which takes a comma delimited list of variables to search for. (variable1,variable2,....), and then searches through each line of the config file, checking if the variable is there, and then printing out the variable found and the value: def displayvar(variables): vardisp = re.compile(r'%s' % (variables.replace(',','|'))) line = configfile.readline() varvalue = re.compile(r'"[^"]*?"$') varname = re.compile(r'".*?"') while line != '': if vardisp.search(line): value = varvalue.search(line) var = varname.search(line) print "%s: %s" % (var.group()[1:-1], value.group()[1:-1]) else: pass line = configfile.readline() There are a few things that are bugging me about this. One is the heavy use of regular expressions, and two is that im using [1.-1] to strip the qoutes. Can anyone point out how to make this more pythonic? Your time is appreciated, Conrad

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