Parsing complex text file in Python

Question

I have a text file like the following:

#some_line
    @another_line
        original_string1|new_string1
#some_other_line
    @and_another_line
        original_string2|new_string2

I want to be able to associate every line with an @ to the preceding line with a #. I cannot seem to figure out a strategy to achieve this in python.

Here is my current code:

    with open(self.file, 'r') as f:
        for i, line in enumerate(f):
            line = line.strip(' \t\n\r')
            if '#' in line[:1]:
                self.parent[i] = line[1:]
            if '@' in line[:1]:
                self.child[i] = line[1:]
            if '|' in line:
                key, value = line.split('|')
                self.strings[key] = value

I need to be able to reference each parent entry and associate the child entries with it. The lines with a '|' also need to be associated with the parent as well.

First, '#' in line[:1] is very odd. Why not just line[0] == '#' or, even better, line.startswith('#')? Are you trying to check something more complicated than that? — abarnert
– abarnert, Commented Aug 13, 2013 at 3:22
Meanwhile… in your data, is there always exactly one @ line for each # line? If so, your code should build parent and child lists that match things up properly. Is that not working? Or do you just not know how to build a mapping out of two parallel lists? — abarnert
– abarnert, Commented Aug 13, 2013 at 3:24
@abarnert: I could use those. Thanks for the suggestion. The basic idea is the just symbolize that line as a line that holds some 'parent' data. — arynhard
– arynhard, Commented Aug 13, 2013 at 3:24
Ah, OK. I think there's enough to answer now. Let me try, and tell me if I got it right. — abarnert
– abarnert, Commented Aug 13, 2013 at 3:26

abarnert · Accepted Answer · 2013-08-13 03:30:03Z

1

I think what you want is a mapping from child strings to parent strings. Or maybe you want a mapping from child strings and parent strings back to line numbers.

So here's what I'll do: build those mappings from strings to line numbers (I'm assuming each one is unique, but it should be easy to fix if not), and also build a mapping from child line numbers to parent line numbers. If you actually needed the string-to-string mapping, or anything else, you should be able to figure it out from this.

The strings-to-line-numbers part is trivial, but for the child-to-parent part, we need to keep track of the last parent line number we've seen.

child_lines, parent_lines, child_parents = {}. {}. {}
last_parent_line = None
with open(self.file) as f:
    for i, line in enumerate(f):
        line = line.strip(' \t\n\r')
        marker, value = line[0], line[1:]
        if marker == '#':
            parent_lines[value] = i
            last_parent_line = i
        elif marker == '@':
            child_lines[value] = i
            child_parents[i] = last_parent_line

That's it.

answered Aug 13, 2013 at 3:30

abarnert

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1 Comment

arynhard Over a year ago

Perfect...I would need string to string reference but I can figure that out. Thanks for showing me how to map things. Appreciate it!

Thierry J · Accepted Answer · 2013-08-13 03:34:52Z

0

This should do the work:

with open(self.file, 'r') as f:
    self.result = {}

    for line in f.readlines():
        line = line.strip()

        if line.startswith("#"):
            parent = line[1:]
            self.result[parent] = {}

        if line.startswith("@"):
            child = line[1:]
            self.result[parent][child] = {}

        if '|' in line:
            key, value = line.split('|')
            self.result[parent][child][key] = value

Then

print self.result
>>> {
    'some_other_line': {
        'and_another_line': {
            'original_string2': 'new_string2'
        }
    },
    'some_line': {
        'another_line': {
            'original_string1': 'new_string1'
        }
    }
}

edited Aug 13, 2013 at 3:34

answered Aug 13, 2013 at 3:28

Thierry J

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1 Comment

abarnert Over a year ago

I think he needs to be able to look up the parent for any given key. This won't do that. But I could be wrong about what he wants…

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