import yaml import pprint def main(): with open('ancestries.yaml') as anc: anc_data = yaml.full_load(anc) with open('heritages.yaml') as her: her_data = yaml.full_load(her) print(anc_data) print(her_data) for i in anc_data['ancestries']: i['heritages'] = [] for j in her_data: print(j) if i['name'] in j['name']: i['heritages'].append(j) pp = pprint.PrettyPrinter(indent=1) pp.pprint(anc_data) final = yaml.safe_dump(anc_data, allow_unicode=True) with open('tmp-ancestriesheritages.yaml', 'w') as f: f.write(final) if __name__ == "__main__": main()