Python使用yaml模块操作YAML文档的方法
牛油菠蘿包 人气:01. YAML简介
YAML是可读性高,用来表达数据序列化格式的,专用于写配置文件的语言。YAML文件其实也是一种配置文件类型,后缀名是.yaml或.yml都可以。其以数据为中心,使用空白,缩进,分行组织数据,从而使得表示更加简洁。
2. 语法规则
- 大小写敏感
- 使用缩进表示层级关系
- 使用空格键缩进,而非Tab键缩进
- 缩进的空格数目不重要,只需要相同层级的元素左侧对齐
- 文件中的字符串不需要使用引号标注,但若字符串包含有特殊字符则需用引号标注
- 注释标识为 #
3. 文件数据结构
对象:键值对的集合(简称"映射或字典")
键值对用冒号 “:” 结构表示 冒号与值之间需用空格分隔
数组:一组按序排列的值(简称"序列或列表")
数组前加有 “-” 符号 符号与值之间需用空格分隔
纯量(scalars):单个的、不可再份的值(如:字符串、bool值、整数、浮点数、时间、日期、null等)
None值可用null,也可用~
表示
4. YAML数据格式示例
# 对象:yaml键值对;即Python中字典 user: 'admin' pwd: 'admin@123' site: "www.yaml.com" # 解析后: {'user': 'admin', 'password': 'admin@123', 'site': 'www.yaml.com'} # 2. 数组:yaml键值对中嵌套数组 user2: - a - b - c user3: - d # 解析后:{'user2':['a','b','c'],'user3':['d']} # 3. 纯量 val_name: name # 字符串: {'val_name': 'name'} spec_val: "name\n" # 特殊字符串: {'spec_val': 'name\n'} pi_val: 3.14 # 数字: {'pi_val': 3.14} bol_val: true # 布尔值: {'bol_val': true} nul_val: null # null值: {'nul_val': None} nul_val: ~ # null值: {'nul_val': None} time_val: 2023-02-03t22:33:22.33-03:00 # 时间值:{'time_val': datetime.datetime(2023, 2, 3, 22, 33, 22, 330000)} date_val: 2024-01-01 # 日期值:{'date_val': datetime.date(2024, 1, 1)} # 4. 引用 name: &name 白云 tester: *name # 相当于 name: 白云 tester: 白云 # 解析后内容:{'name': '白云', 'tester': '白云'} # 5. 强制转换 str: !!str 3.14 int: !!int "666" # 输出: {'str': '3.14','int': 123}
5. 安装yaml库
pip install pyyaml
6. 读取YAML
6.1 读取键值对或嵌套键值对
yaml文件内容为:
user1: name: xm stu: 101 user2: name: xh stu: 102 user3: name: xl stu: 103
程序代码:
import yaml import os class ReadYAML(object): def read_yaml(self,yaml_file): with open(yaml_file,'r',encoding='utf-8') as f: file_data = f.read() print("file_data类型:",type(file_data)) data = yaml.safe_load(file_data) print("data类型:",type(data)) return data if __name__ == "__main__": base_name = os.path.dirname(os.path.realpath(__file__)) yaml_path = os.path.join(base_name,'test.yaml') ry = ReadYAML() res = ry.read_yaml(yaml_path) print(res)
输出结果:
file_data类型: <class 'str'>
data类型: <class 'dict'>
{'user1': {'name': 'xm', 'stu': 101}, 'user2': {'name': 'xh', 'stu': 102}, 'user3': {'name': 'xl', 'stu': 103}}
6.2 读取数组类型
yaml文件内容为:
class1: - stu1 - stu2 - stu3 class2: - stu2
程序代码:
import yaml import os class ReadArraysYAML(object): def read_yaml(self,yaml_file): with open(yaml_file,'r',encoding='utf-8') as f: file_data = f.read() # print("file_data类型:",type(file_data)) data = yaml.safe_load(file_data) # print("data类型:",type(data)) return data if __name__ == "__main__": base_name = os.path.dirname(os.path.realpath(__file__)) yaml_path = os.path.join(base_name,'arrays.yaml') ry = ReadArraysYAML() res = ry.read_yaml(yaml_path) print(res)
输出结果:
{'class1': ['stu1', 'stu2', 'stu3'], 'class2': ['stu2']}
6.3 多文档同在一份yaml文件中时的读取方法
yaml文件内容:
# 分段yaml文件中存在多个文档 --- animal1: dog age: 1 --- animal2: cat age: 2
程序代码:
""" 多文档同在一份yaml文件中时的读取方法(使用yaml.safe_load_all()) """ import yaml import os def get_yaml_load_all(yaml_file): file = open(yaml_file,'r',encoding='utf-8') file_data = file.read() file.close() all_data = yaml.safe_load_all(file_data) for data in all_data: print(data) if __name__ == "__main__": current_path = os.path.dirname(__file__) print(current_path) yaml_path = os.path.join(current_path,'muti.yaml') get_yaml_load_all(yaml_path)
输出结果:
d:\PyProject\YAML
{'animal1': 'dog', 'age': 1}
{'animal2': 'cat', 'age': 2}
6.4 向YAML文档写入
程序代码:
""" 使用yaml.dump()方法将列表或字典数据写入进已存在的yaml文档 """ import yaml import os def generate_yaml_doc(yaml_file): py_object = {'school':'Fxxking U','student':['stu1','stu2']} file = open(yaml_file,'w',encoding='utf-8') yaml.safe_dump(py_object,file) file.close() if __name__ == "__main__": current_path = os.path.dirname(__file__) print(current_path) yaml_path = os.path.join(current_path,'generateYAML.yaml') generate_yaml_doc(yaml_path)
写入后,YAML文档内容:
school: Fxxking U student: - stu1 - stu2
注:若想要以追加的形式写入,只需将open()中的’w’改为’a’即可
6.5 更新/修改 YAML文件内容
修改前YAML文件内容:
school: Fxxking U student: - stu1 - stu2
程序代码:
import yaml import os from readArraysYAML import ReadArraysYAML def update_yaml(k,v,yaml_file): readY = ReadArraysYAML() old_data = readY.read_yaml(yaml_file) old_data[k] = v # 修改读取的数据,如果k不存在则新增一组键值对 with open(yaml_file,'w',encoding='utf-8') as f: yaml.safe_dump(old_data,f) if __name__ == "__main__": current_path = os.path.dirname(__file__) yaml_path = os.path.join(current_path,'generateYAML.yaml') k = 'school' v = 'SZ U' update_yaml(k,v,yaml_path)
修改后,YAML文件内容:
school: SZ U student: - stu1 - stu2
7. 使用ruamel模块将数据转换为标准的yaml内容
安装ruamel库
pip install ruamel.yaml
程序代码:
from ruamel import yaml import os def generate_yaml_doc_ruamel(yaml_file): py_object = {'file_type':'ruamel_yaml','school':'Fxxking U','student':['c','d']} with open(yaml_file,'w',encoding='utf-8') as f: yaml.dump(py_object,f,Dumper=yaml.RoundTripDumper) if __name__ == "__main__": current_path = os.path.dirname(__file__) yaml_path = os.path.join(current_path,'ruamelGenerateYAML.yaml') generate_yaml_doc_ruamel(yaml_path) print("写入成功!")
写入后,YAML文件内容:
file_type: ruamel_yaml school: Fxxking U student: - c - d
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