# Sample code for custom evaluation

**URL:** <https://discuss.ray.io/t/sample-code-for-custom-evaluation/4001>\
**Category:** Ray Tune\
**Created:** [October 31, 2021, 11:38pm UTC](https://discuss.ray.io/t/sample-code-for-custom-evaluation/4001 "2021-10-31T23:38:56Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![narik11](https://avatars.discourse-cdn.com/v4/letter/n/cc9497/32.png) [@narik11](https://discuss.ray.io/u/narik11)\
**Post date:** [October 31, 2021, 11:38pm UTC](https://discuss.ray.io/t/sample-code-for-custom-evaluation/4001/1 "2021-10-31T23:38:56Z")

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Hi, The custom eval exmaple failed [[https://github.com/ray-project/ray/blob/master/rllib/examples/custom\_eval.py](https://github.com/ray-project/ray/blob/master/rllib/examples/custom_eval.py)] when “evaluation\_num\_workers” = 1

> File “ppo\_Training.py”, line 78, in custom\_eval\_function  
> worker\_1.foreach\_env.remote(lambda env: env.set\_intermediate\_flags(True, True, validationSeed, validationTrial))  
> AttributeError: ‘list’ object has no attribute ‘foreach\_env’

could anyone please provide a sample code, such that it works with one eval worker.