# Define a user proposal distribution in Metropolis

**URL:** <https://discourse.pymc.io/t/define-a-user-proposal-distribution-in-metropolis/4736>\
**Category:** Questions\
**Created:** [March 24, 2020, 10:03pm UTC](https://discourse.pymc.io/t/define-a-user-proposal-distribution-in-metropolis/4736 "2020-03-24T22:03:03Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Konstantin\_Kuznetsov](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/konstantin_kuznetsov/32/2535_2.png) [@Konstantin\_Kuznetsov](https://discourse.pymc.io/u/Konstantin_Kuznetsov)\
**Post date:** [March 24, 2020, 10:03pm UTC](https://discourse.pymc.io/t/define-a-user-proposal-distribution-in-metropolis/4736/1 "2020-03-24T22:03:03Z")

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Hello!

I would like to use user defined proposal distribution (not reversable) in Metropolis sampler. Could you help me with implementation of this or give me some key maybe.  
I found something close in documentation for PyMC2 [https://pymc-devs.github.io/pymc/extending.html](https://pymc-devs.github.io/pymc/extending.html) But I believe this approach would not work in PyMC3.  
Thanks for help.