[Python] Prevent ruamel.yaml from touching unchanged lines when round-trip dumping YAML

I’m automating small edits to YAML files (and opening PRs), but I need only the lines I intentionally changed to appear in the diff—yet ruamel.yaml still rewrites lines I never touched. For example, whitespace around colons, blank-line indentation, flow-sequence commas, comments and other punctuation get normalized even though my code only mutates a single key.

Here’s a minimal example of my workflow:

from ruamel.yaml import YAML

yaml = YAML(typ='rt')
yaml.preserve_quotes = True # keeps single-quoted scalars unchanged
yaml.width = 4096 # disables automatic line-wrapping

# 1) Load original YAML
with open('config.yml') as f:
data = yaml.load(f)

# 2) Mutate just one field
data['policy']['enabled'] = True

# 3) Overwrite the same file
with open('config.yml', 'w') as f:
yaml.dump(data, f)


preserve_quotes and width helped me in some cases like long lines that were folded and single quotes that were changed, but there are still a lot of unwanted remaining changes:

• Colon-spacing normalized

name : prepaid_underbill_corrections

changed to:

name: prepaid_underbill_corrections

• Flow-sequence spacing inserted

["a","b","c"]

changed to:

["a", "b", "c"]

• 
  Blank lines with indentations - indentations are removed
  
  
• 
  Other cosmetic tweaks on untouched lines (comments, trailing spaces, etc.)
  

My goal: Only rewrite the YAML lines corresponding to the keys/values I actually changed, and leave every other line, including the spaces around punctuation, blank-line indentation, flow-sequence commas, comments, and anchors completely untouched.

Questions:

1. 
   Is there a built-in ruamel.yaml configuration (loader/dumper flags, representer hooks, etc.) that disables all remaining punctuation or whitespace normalization on untouched nodes?
   
   
2. 
   If not, what’s the most elegant, “library-supported” pattern to achieve truly zero-collateral edits? For example, diff-and-patch, custom emitter hooks, or another approach in the round-trip API I may have missed?
   
   Any pointers or code examples to help me produce PRs that contain only my intended changes would be hugely appreciated!
   

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