python - Parsing YAML, return with line number

Question

I'm making a document generator from YAML data, which would specify which line of the YAML file each item is generated from. What is the best way to do this? So if the YAML file is like this:

- key1: item 1
  key2: item 2
- key1: another item 1
  key2: another item 2

I want something like this:

[
     {'__line__': 1, 'key1': 'item 1', 'key2': 'item 2'},
     {'__line__': 3, 'key1': 'another item 1', 'key2': 'another item 2'},
]

I'm currently using PyYAML, but any other library is OK if I can use it from Python.

Answer 1

I've made it by adding hooks to Composer.compose_node and Constructor.construct_mapping:

import yaml
from yaml.composer import Composer
from yaml.constructor import Constructor

def main():
    loader = yaml.Loader(open('data.yml').read())
    def compose_node(parent, index):
        # the line number where the previous token has ended (plus empty lines)
        line = loader.line
        node = Composer.compose_node(loader, parent, index)
        node.__line__ = line + 1
        return node
    def construct_mapping(node, deep=False):
        mapping = Constructor.construct_mapping(loader, node, deep=deep)
        mapping['__line__'] = node.__line__
        return mapping
    loader.compose_node = compose_node
    loader.construct_mapping = construct_mapping
    data = loader.get_single_data()
    print(data)