Parsing files with python

Question

My input file is going to be something like this

key "value"
key "value"
... the above lines repeat

What I do is read the file contents, populate an object with the data and return it. There are only a set number of keys that can be present in the file. Since I am a beginner in python, I feel that my code to read the file is not that good

My code is something like this

ObjInstance = CustomClass()
fields = ['key1', 'key2', 'key3']

    for field in fields:
        for line in f:
            if line.find(field) >= 0:
                if pgn_field == 'key1':
                    objInstance.DataOne = get_value_using_re(line)
                elif pgn_field == 'key2':
                    objInstance.DataTwo = get_value_using_re(line)

return objInstance;

The function "get_value_using_re" is very simple, it looks for a string in between the double quotes and returns it.

I fear that I will have multiple if elif statements and I don't know if this is the right way or not.

Am I doing the right thing here?

Answer 1

A normal approach in Python would be something like:

for line in f:
    mo = re.match(r'^(\S+)\s+"(.*?)"\s*$')
    if not mo: continue
    key, value = mo.groups()
    setattr(objInstance, key, value)

If the key is not the right attribute name, in the last line line in lieu of key you might use something like translate.get(key, 'other') for some appropriate dict translate.

Answer 2

I'd suggest looking at the YAML parser for python. It can conveniently read a file very similar to that and input it into a python dictionary. With the YAML parser:

import yaml
map = yaml.load(file(filename))

Then you can access it like a normal dictionary with map[key] returning value. The yaml files would look like this:

key1: 'value'
key2: 'value'

This does require that all the keys be unique.