model.Write "Unknown file type" with json

Answered

Kati Moug

June 19, 2020 21:24

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I'm able to use model.write('test.lp') and model.write('test.sol') but not model.write('test.attr') or model.write('test.json'). The error message is " GurobiError: Unknown file type for file 'test.attr' " Anyone have any idea why this may be the case? I'm using Gurobi 8.1 with Python and the model is solved to optimality.

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 03:11 Edited

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum. Or why not try our AI Gurobot?.
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  Eli Towle

  • Gurobi Staff

  June 19, 2020 21:47

  Hi Kati,

  Gurobi 9.0.0 was the first version to support writing .attr and .json files. Could you upgrade to the latest version of Gurobi (9.0.2) and try again?

  Thanks,

  Eli

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• 

  Robert Hildebrand

  August 31, 2022 18:34 Edited

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  I updated to Gurobi 9.5.2, but I am getting the same error with writing the log file:

  I can run 

  m.write("myfile.sol")
  m.write("myfile.lp")
  m.write("myfile.log")

  But then I get the error

  GurobiError: Unknown file type for file 'myfile.log'

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  Robert Hildebrand

  August 31, 2022 18:37

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  I see.  I can write it by using 

  m.Params.logfile = "myfile.log"

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