Passing paths to python variables  #439

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1. EthanMarx

   added

   enhancementNew feature or requestNew feature or request

   on Jan 26, 2024
2. mauvilsa commented on Jan 29, 2024

   

   mauvilsa

   on Jan 29, 2024

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   Thank you for the proposal! It is an interesting idea. I need to think about it to see if it could have unexpected consequences. One small comment for now. One thing is that when parsing, an import path resolves to its corresponding value. This might be relatively easy to implement.

   A more complex behavior that people could ask for could be that additionally when serializing (dump, save, print_config), the import path is preserved. This would be considerably complex an not be implemented any time soon.
3. EthanMarx commented on May 28, 2025

   

   EthanMarx

   on May 28, 2025

   Last edited by EthanMarx

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   @mauvilsa is there any update on this? Or, is there a simple way to specify e.g. math.pi in a jsonargparse yaml config that will be parsed as a float?
4. mauvilsa commented on Jul 26, 2025

   

   mauvilsa

   on Jul 26, 2025

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   I am not sure if it justifies investing effort in implementing this. If the feature request includes being able to serialize back into the variable path, then it is rather complex. And if it is only for parsing, then the use is quite limited since there aren't many predefined constants to choose from. And just thinking of pi I would imagine very likely people would also want fractions of pi.

   One option which is more general could be to use an OmegaConf resolver, that is:

   from jsonargparse import ArgumentParser
   from omegaconf import OmegaConf
   import math
   
   # define a custom resolver
   def const(expr: str):
       allowed = {"pi": math.pi, "e": math.e}
       # evaluate expression in a safe namespace
       return eval(expr, {"__builtins__": None}, allowed)
   
   OmegaConf.register_new_resolver("const", const)
   
   parser = ArgumentParser(parser_mode="omegaconf")
   parser.add_argument("--config", action="config")
   parser.add_argument("--value", type=float)
   print(parser.parse_args())

   With this, you could have in a config file value: ${const:pi} and also fractions value: ${const:3*pi/4}. Though, this only works in config files, not when given through argument --value.
5. mauvilsa

   added

   pending author responseA question was asked or some work is pendingA question was asked or some work is pending

   on Aug 22, 2025
6. mauvilsa commented on Aug 29, 2025

   

   mauvilsa

   on Aug 29, 2025

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   In pull request #765 there is a new experimental implementation omegaconf+ that supports interpolation across config files and command line arguments.
7. mauvilsa commented on Aug 29, 2025

   

   mauvilsa

   on Aug 29, 2025

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   If you want actual import paths to variables, you could also implement it with an omegaconf resolver. So I will be marking this issue to be resolved by #765.
8. mauvilsa

   closed this as completedin #765on Aug 29, 2025