# PyStan: RuntimeError: Initialization Failed

**URL:** <https://discourse.mc-stan.org/t/pystan-runtimeerror-initialization-failed/3699>\
**Category:** Modeling\
**Created:** [March 27, 2018, 9:30pm UTC](https://discourse.mc-stan.org/t/pystan-runtimeerror-initialization-failed/3699 "2018-03-27T21:30:58Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![patrickjmc](https://avatars.discourse-cdn.com/v4/letter/p/439d5e/32.png) [@patrickjmc](https://discourse.mc-stan.org/u/patrickjmc)\
**Post date:** [March 28, 2018, 2:17pm UTC](https://discourse.mc-stan.org/t/pystan-runtimeerror-initialization-failed/3699/5 "2018-03-28T14:17:49Z")

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With some sleep I figured it out. in the comments of my program I define

```
int<lower=1000> K[N]; // initial trials
int<lower=10000> y[N]; // initial successes

```

but when I declare my data, I swapped K and y: y \> K.  
Simple user error :)

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