# No way to pin build dependencies

**URL:** <https://discuss.python.org/t/no-way-to-pin-build-dependencies/29833>\
**Category:** Packaging\
**Tags:** help\
**Created:** [July 17, 2023, 10:18pm UTC](https://discuss.python.org/t/no-way-to-pin-build-dependencies/29833 "2023-07-17T22:18:07Z")\
**Posts on this page:** 1\
**Showing post:** 14

<div class="post-metadata">

**Author:** ![JoeJasinski](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/joejasinski/32/13550_2.png) [@JoeJasinski](https://discuss.python.org/u/JoeJasinski)\
**Post date:** [July 18, 2023, 3:20pm UTC](https://discuss.python.org/t/no-way-to-pin-build-dependencies/29833/14 "2023-07-18T15:20:12Z")

</div>

I’m still looking at this, but the constraints file doesn’t seem to be taking effect for the build.

For example, if I run the following with verbose turned on.

```auto
echo "statsmodels==0.13.2" >> constraints.txt
echo "Cython==0.29.27" >> constraints.txt 
pip install -v statsmodels==0.13.2 -c constraints.txt 

```

It looks like cython 3.0.0 is somehow making it in there.

```auto
Successfully installed cython-3.0.0 numpy-1.14.5 oldest-supported-numpy-2022.11.19 scipy-1.7.3 setuptools-68.0.0 wheel-0.40.0

```

Same thing happens if I’m less strict about the version and specify cython less than 3.

```auto
echo "statsmodels==0.13.2" >> constraints.txt
echo "Cython<3" >> constraints.txt 
pip install -v statsmodels==0.13.2 -c constraints.txt 

```

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_[View the full topic](https://discuss.python.org/t/no-way-to-pin-build-dependencies/29833)._