Code:
import yaml
import os
import re

with open("test.yaml", 'r') as stream:
    try:
        loaded=stream.read()
    except yaml.YAMLError as exc:
        print(exc)

with open("modified.yaml", 'w') as stream:
    try:
        yaml.dump(re.sub(r'anotherName: [^\n]*', 'anotherName: somethingChanged', loaded), stream)
    except yaml.YAMLError as exc:
        print(exc)

OUTPUT:

cat modified.yaml
"---\nkind: test\nscope: not far\nspec:\n  test1:\n    options:\n      - name: test.com\n\
  \        anotherName: somethingChanged\n        empty: []\n    groupOne: []\n  \
  \  emptyList:\n      firstList: []\n      secondList: []"