import yamldata = dict( A = 'a', B = dict( C = 'c', D = 'd', E = 'e', ))with open('data.yml', 'w') as outfile: yaml.dump(data, outfile, default_flow_style=False)该
default_flow_style=False参数对于产生所需的格式（流样式）是必需的，否则对于嵌套集合，它将产生块样式：
A: aB: {C: c, D: d, E: e}
