No easy way to get an isolated, customized SafeLoader

In all docs and example code I have seen, developers are instructed to register loaders and dumpers as:

import yaml
yaml.SafeLoader.add_constructor(...)

This works and is simple. However, it does not scale to the situation where a single process might want different loaders/dumpers , e.g. scenarios like

• one yaml tag set for a configuration file and another for saved state,
• a base project that uses pyyaml and has an in-process plugin system, and I’m writing a plugin that wants to use pyyaml for something else

The only workaround I have found is to do

import importlib
import yaml.constructor as yamlConstructor
import yaml.loader as yamlLoader
import yaml.dumper as yamlDumper
import yaml.representer as yamlRepresenter
yamlConstructor = importlib.reload(yamlConstructor)
yamlRepresenter = importlib.reload(yamlRepresenter)
yamlLoader = importlib.reload(yamlLoader)
MyLoader = yamlLoader.SafeLoader
MyDumper = yamlDumper.SafeDumper

MyLoader.add_constructor(...)

which is pretty awful, and may break other code later it has been written to expect the static behaviour in accessing yaml.SafeLoader directly.

My feature request is for to be able to do something like

import yaml
MyLoader = yaml.buildSafeLoader()

MyLoader.add_constructor(...)

which allows me to easily avoid the static configuration issues above.

[akdor1154]

For sure that sounds like something to avoid, but everyone I have seen using pyyaml is using it that way. The docs say to register constructors that way (using yaml.add_constructor, which is a top level module function that seems to work in this modify-built-in-classes way by default), and the top rated answers on stack overflow also recommend that developers do it that way. Maybe this could be considered a documentation bug then?

[timcharper]

It does! Thank you 😃