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tech_docs/python/YAML_python.md

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+YAML, a recursive acronym for "YAML Ain't Markup Language," is a human-readable data serialization standard that can be used in conjunction with all programming languages and is often used for writing configuration files. While Python does not include a built-in library for YAML, the third-party library `PyYAML` is widely used for parsing and generating YAML files.
+
+### PyYAML Usage Guide
+
+#### Installation
+PyYAML can be installed via pip. It's straightforward to add to your project:
+```sh
+pip install PyYAML
+```
+
+### Basic Operations
+
+#### Loading YAML
+
+PyYAML provides functions like `yaml.load()` and `yaml.safe_load()` to parse YAML from a string or file. The `safe_load()` function is recommended for loading untrusted input to avoid executing arbitrary Python objects.
+
+##### Parsing YAML from a String
+```python
+import yaml
+
+yaml_string = """
+- hero:
+    name: John Doe
+    age: 30
+- villain:
+    name: Jane Doe
+    age: 25
+"""
+
+data = yaml.safe_load(yaml_string)
+print(data)
+```
+
+##### Reading YAML from a File
+```python
+with open('data.yaml', 'r') as file:
+    data = yaml.safe_load(file)
+    print(data)
+```
+
+#### Dumping YAML
+
+To serialize Python objects into a YAML string or file, use `yaml.dump()`.
+
+##### Converting Python Object to YAML String
+```python
+data = {
+    'hero': {'name': 'John Doe', 'age': 30},
+    'villain': {'name': 'Jane Doe', 'age': 25}
+}
+
+yaml_string = yaml.dump(data)
+print(yaml_string)
+```
+
+##### Writing YAML Data to a File
+```python
+with open('output.yaml', 'w') as file:
+    yaml.dump(data, file)
+```
+
+### Advanced Usage
+
+#### Custom Python Objects
+
+PyYAML can serialize and deserialize custom Python objects through constructors and representers.
+
+##### Serializing Custom Objects
+```python
+class Hero:
+    def __init__(self, name, age):
+        self.name = name
+        self.age = age
+
+yaml.add_representer(Hero, lambda dumper, obj: dumper.represent_dict({'name': obj.name, 'age': obj.age}))
+
+hero = Hero("John Doe", 30)
+print(yaml.dump(hero))
+```
+
+##### Deserializing Custom Objects
+```python
+def hero_constructor(loader, node):
+    fields = loader.construct_mapping(node)
+    return Hero(**fields)
+
+yaml.add_constructor('!Hero', hero_constructor)
+
+yaml_string = "!Hero {name: John Doe, age: 30}"
+hero = yaml.safe_load(yaml_string)
+print(hero.name, hero.age)
+```
+
+### Use Cases
+
+- **Configuration Files**: YAML's readability makes it ideal for configuration files used in applications and services.
+
+- **Data Serialization**: YAML is useful for serializing complex data structures, such as trees or objects, in a format that can be edited by humans.
+
+- **Infrastructure as Code (IaC)**: In DevOps, YAML is commonly used to define and manage infrastructure through code for cloud services, container orchestration (like Kubernetes), and automation tools.
+
+### Best Practices
+
+- **Use `safe_load()`**: Always prefer `safe_load()` over `load()` when parsing YAML to avoid executing arbitrary Python objects contained within the YAML file.
+
+- **Keep It Simple**: Although YAML supports complex structures, maintaining simplicity in your YAML documents ensures they remain readable and maintainable.
+
+- **Indentation**: Pay attention to indentation, as it is significant in YAML and a common source of errors.
+
+PyYAML provides a powerful interface for working with YAML in Python, combining the flexibility of YAML with the expressiveness of Python. Whether you're configuring software, defining infrastructure, or simply need a readable format for data serialization, PyYAML equips you with the tools necessary to work effectively with YAML data.