Extract and replace text matching multi-line pattern after keyword

Question

I am trying to transform a yaml document in order to make it easier to parse later in my project. I have output that looks like this:

I want to use regex to find all occurrences of:

  Export:
     Name: xxxxx

But only those occurrences which appear after "Output:"

My document looks something like this:

Resources: 
  MyResource: Resource 1
  Export: 
    Name: Some undesired export name
Outputs:
  ExportOne:
    Description: Notes about export #1 here
    Export:
      Name: Desired export #1
  ExportTwo: 
    Description: Notes about export #2 here
    Export:
      Name: Desired export #2

So far no matter what I have tried I only capture one of the "Export: Name:" occurrences.

After finding the aforementioned text my goal is to change it to

ExportName: <existing value>

I am using python for this project, so far the regular expressions I have tried have all been variations of:

(?s)(?<=Outputs:)(.+(Export:.*?Name:)+)

Any advice on how to do this... or a better way to perform this transformation?

Thanks!

Answer 1

I suppose from your tags that the input file is YAML. It would be better to use a YAML library for parsing and modifying the file. Using regular expressions is also possible, but not the best solution for me.

You have a missing space in your input file "MyResource: Res1".

Here is an example:

pip install pyyaml

import yaml

# Read from a file
def read_yaml(filename):
    with open(filename, 'r') as file:
        yaml_data = yaml.safe_load(file)
        return yaml_data


# Find and replace values
def modify_data(yaml_data):
    for output in yaml_data['Outputs'].values():
        if 'Export' in output and 'Name' in output['Export']:
            name = output['Export']['Name']
            output['ExportName'] = name
            del output['Export']
    return yaml_data

# Write to a file
def save_yaml(filename, yaml_data):
    with open(filename, 'w') as file:
        yaml.dump(yaml_data, file, sort_keys=False)

if __name__ == '__main__':
    data = read_yaml('input.yaml')
    modified_data = modify_data(data)
    save_yaml('output.yaml', modified_data)

python main.py && cat output.yaml
Resources:
  MyResource: Res1
  Export:
    Name: SomeName
Outputs:
  ExportOne:
    ExportName: abc
  ExportTwo:
    ExportName: def

If you need to parse YAML v1.2 or later check the @Anthon answer.

Other yaml parsers that can be used: ruamel.yaml, strictyaml, poyo