Parsing specificly named list in a .py file using python

Question

I just want to check if there is any better way of doing this rather than using what i came up with.

The thing is that i need to parse a .py file, more precisely i have to look for a specific list named id_list that contains several int numbers. Numbers can be written in several formats.

For example:

id_list = [123456, 789123, 456789]

id_list = [    123456,
               789123,
               456789    ]

id_list = [    123456
               ,789123
               ,456789    ]

What i came up with works just fine, but for the sake of perfectionism i want to know if there is "smoother" way of doing so.

with open(filepath, 'rb') as input_file:
    parsed_string = ''
    start_flag = False
    start_parsing = False
    for line in input_file:
        if 'id_list' in line:
            id_detected = True
        if id_detected:
            for char in line:
                if char == '[':
                    start_parsing = True
                if start_parsing and char != '\n':
                    parsed_string += char
                if char == ']':
                    id_detected = False
                    start_parsing = False
                    break

After that has been done im just filtering parsed_string:

new_string = "".join(filter(lambda char: char.isdigit() or char == ',', parsed_string))

Which gets me string containing numbers and commas: 123456,789123,456789

So to wrap this up, is there anything that i could improve?

What about id_list = list()? Or x = [] then id_list = x? — cdarke
– cdarke, Commented Nov 28, 2016 at 8:05
@jonrsharpe Not quite sure if i should do that because there are a lot of files that needs to be parsed, importing all of them at once wouldn't be a good idea i suppose. — Sir DrinksCoffeeALot
– Sir DrinksCoffeeALot, Commented Nov 28, 2016 at 8:08
How come? Could you give some more context? Do these things change frequently? How do they get into the Python files to begin with? — jonrsharpe
– jonrsharpe, Commented Nov 28, 2016 at 8:09
If this is a one-time process, just use import and store a mapping in a more easily accessible format. Don't do it on every search, that's not efficient. It's not really clear why your output is a string, either; a list or set of IDs would be more usable, surely? — jonrsharpe
– jonrsharpe, Commented Nov 28, 2016 at 9:12

Fomalhaut · Accepted Answer · 2016-11-28 08:27:23Z

2

You can use a regular expression to solve:

import re

with open(filepath, 'rb') as input_file:
    text = input_file.read()
    match = re.search(r'id_list\s*=\s*\[(.*?)\]', text, flags=re.DOTALL)

    if match is None:
        print "Not found"

    else:
        id_list_str = match.group(1)
        id_list = map(int, id_list_str.split(','))
        print id_list

edited Nov 28, 2016 at 8:27

answered Nov 28, 2016 at 8:11

Fomalhaut

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2 Comments

PM 2Ring Over a year ago

eval and exec should generally be avoided because they can be a security risk. For details, please see Eval really is dangerous by SO veteran Ned Batchelder. Instead, you can use the safer alternative: ast.literal_eval.

PM 2Ring Over a year ago

Manually parsing the data is definitely much safer!

Ajay Pal · Accepted Answer · 2016-11-28 08:26:02Z

0

just use import and from

If you don't want to import the whole python files just import the elements you need

example

from filename.py import id_list

answered Nov 28, 2016 at 8:26

Ajay Pal

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