# Pickle error while using lambda function

**URL:** <https://discourse.pymc.io/t/pickle-error-while-using-lambda-function/3151>\
**Category:** Questions\
**Created:** [April 24, 2019, 5:20pm UTC](https://discourse.pymc.io/t/pickle-error-while-using-lambda-function/3151 "2019-04-24T17:20:56Z")\
**Posts on this page:** 1\
**Showing post:** 18

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**Author:** ![avi](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/avi/32/1700_2.png) [@avi](https://discourse.pymc.io/u/avi)\
**Post date:** [April 30, 2019, 12:53pm UTC](https://discourse.pymc.io/t/pickle-error-while-using-lambda-function/3151/18 "2019-04-30T12:53:30Z")

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Please see this thread and let me know if this helps

> [@When I am custom likelihood example I get pickle error when multiple chains are used](https://discourse.pymc.io/t/when-i-am-custom-likelihood-example-i-get-pickle-error-when-multiple-chains-are-used/3062):
>
> Hello Everyone, I am trying to use this example ([[https://docs.pymc.io/notebooks/blackbox\_external\_likelihood.html](https://docs.pymc.io/notebooks/blackbox_external_likelihood.html)]([http://Black](http://Black) Box Example))) without gradient part. However, I get the pickling error when using lambda function and number of chains \> 1. Could some body please point me to the correct direction? When I read though various messages on this forum, it has been suggested that the latest version fixes the problem. I am using the latest version from the repo. I am on Windows 10 and u…

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