Parsing YAML with Custom Data Types in Python Using PyYAML - implementing Loaders
I'm working on a project and hit a roadblock. I'm trying to parse a YAML file that includes custom data types defined in the document, specifically a date format that isn't standard. When I attempt to load the YAML using PyYAML, I'm running into issues where the custom date strings are not being recognized and are instead being loaded as plain strings. Here's a snippet of my YAML file: ```yaml custom_date: !!my_date '2023-10-01' ``` I defined a custom YAML loader to handle the `!!my_date` tag, but it doesn't seem to be invoked during loading. Here is my custom loader implementation: ```python import yaml from datetime import datetime class MyDateLoader(yaml.Loader): def construct_my_date(self, node): value = self.construct_scalar(node) return datetime.strptime(value, '%Y-%m-%d') def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self.add_constructor('!my_date', self.construct_my_date) ``` And here is how I'm trying to load the YAML file: ```python with open('data.yaml', 'r') as file: data = yaml.load(file, Loader=MyDateLoader) ``` When I print `data`, the `custom_date` key still shows up as a plain string instead of a `datetime` object. I even tried using `yaml.safe_load`, but that raises an behavior since it doesn't allow custom types. The behavior messages I receive don’t provide much insight, just that the type was not recognized. I’m using PyYAML version 5.4.1. Any ideas on why my custom constructor isn't being triggered? Is there a better approach to handle custom data types in YAML with PyYAML? My development environment is macOS. What's the best practice here? Am I approaching this the right way? I recently upgraded to Python 3.9. Is this even possible?