# \`using Pycall\` on Google Colab makes Julia runtime crash

**URL:** <https://discourse.julialang.org/t/using-pycall-on-google-colab-makes-julia-runtime-crash/136718>\
**Category:** New to Julia\
**Tags:** question, pycall, colab\
**Created:** [April 15, 2026, 2:50am UTC](https://discourse.julialang.org/t/using-pycall-on-google-colab-makes-julia-runtime-crash/136718 "2026-04-15T02:50:01Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![funatsufumiya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/funatsufumiya/32/221561_2.png) [@funatsufumiya](https://discourse.julialang.org/u/funatsufumiya)\
**Post date:** [April 15, 2026, 2:50am UTC](https://discourse.julialang.org/t/using-pycall-on-google-colab-makes-julia-runtime-crash/136718/1 "2026-04-15T02:50:01Z")

</div>

I’d like to use PyCall on Google Colab Julia runtime, but not succeeded.

`import Pkg; Pkg.add("PyCall")` works, however, `using PyCall` would crash.

`run(`which python`)` shows `/usr/local/bin/python`, `run(`which pip`)` shows `/usr/local/bin/pip`.

Log:

```julia
using PyCall

```

```txt
[4775] signal 11 (1): Segmentation fault
in expression starting at none:1
PyObject_GC_Del at /usr/lib/x86_64-linux-gnu/libpython3.12.so.1.0 (unknown line)
unknown function (ip: 0x7b351392224c)
pydecref_ at /root/.julia/packages/PyCall/1gn3u/src/PyCall.jl:118
pydecref at /root/.julia/packages/PyCall/1gn3u/src/PyCall.jl:123
jfptr_pydecref_4467 at /root/.julia/compiled/v1.11/PyCall/GkzkC_0abgj.so (unknown line)
run_finalizer at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/gc.c:303
jl_gc_run_finalizers_in_list at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/gc.c:393
run_finalizers at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/gc.c:439
jl_mutex_unlock at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/julia_locks.h:80 [inlined]
jl_generate_fptr_impl at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/jitlayers.cpp:545
jl_compile_method_internal at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/gf.c:2536 [inlined]
jl_compile_method_internal at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/gf.c:2423
ijl_compile_method_instance at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/gf.c:2860
ijl_compile_hint at /cache/build/tester-amdci5-12/julialang/julia-release-1-dot-11/src/gf.c:2873

```

I also tried below, but nothing fixed.

```julia
ENV["PYTHON"] = "/usr/local/bin/python"
import Pkg; Pkg.add("PyCall"); Pkg.build("PyCall")

```

---

<div class="post-metadata">

**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [April 15, 2026, 4:10am UTC](https://discourse.julialang.org/t/using-pycall-on-google-colab-makes-julia-runtime-crash/136718/2 "2026-04-15T04:10:42Z")

</div>

Either use PythonCall.jl , or start Julia single threaded:

```bash
julia -t 1,0

```

---

<div class="post-metadata">

**Author:** ![funatsufumiya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/funatsufumiya/32/221561_2.png) [@funatsufumiya](https://discourse.julialang.org/u/funatsufumiya)\
**Post date:** [April 15, 2026, 4:23am UTC](https://discourse.julialang.org/t/using-pycall-on-google-colab-makes-julia-runtime-crash/136718/3 "2026-04-15T04:23:29Z")

</div>

Thank you! PythonCall is working now. I’ll try Julia single threaded also 🙂

---

<div class="post-metadata">

**Author:** ![funatsufumiya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/funatsufumiya/32/221561_2.png) [@funatsufumiya](https://discourse.julialang.org/u/funatsufumiya)\
**Post date:** [April 15, 2026, 4:51am UTC](https://discourse.julialang.org/t/using-pycall-on-google-colab-makes-julia-runtime-crash/136718/4 "2026-04-15T04:51:22Z")

</div>

Solved. Not using default Julia runtime, but creating custom runtime with single threaded solved this problem. Now PyCall worked. Thank you very much!!

`julia-jupyter-install.ipynb`:

```julia-auto
{
  "nbformat": 4,
  "nbformat_minor": 0,
  "metadata": {
    "colab": {
      "name": "julia-jupyter-install.ipynb",
      "provenance": [],
      "collapsed_sections": []
    },
    "kernelspec": {
      "name": "julia-1.11",
      "display_name": "julia-1.11"
    }
  },
  "cells": [
    {
      "cell_type": "code",
      "metadata": {
        "id": "CN08w8uiICa8",
        "colab_type": "code",
        "colab": {}
      },

      "source": [
        "#!curl -sSL \"https://julialang-s3.julialang.org/bin/linux/x64/1.11/julia-1.11.5-linux-x86_64.tar.gz\" -o julia.tar.gz\n",
        "#!tar -xzf julia.tar.gz -C /usr --strip-components 1\n",
        "#!rm -rf julia.tar.gz*\n",
        "!julia -e 'using Pkg; Pkg.add(\"IJulia\")'\n",
        "!echo \"Installing IJulia kernel...\"\n",
        "!julia -e 'using IJulia; IJulia.installkernel(\"julia\", env=Dict(\"JULIA_NUM_THREADS\"=>\"1\"))'"
      ],
      "execution_count": 0,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "sGOaN98-IZxj",
        "colab_type": "text"
      },
      "source": [
        "After executing the above with Shift+Enter, click \"Runtime\" > \"Change Runtime Type\" > \"Save.\" and restart runtime."
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "id": "ls5Cl0hsIndc",
        "colab_type": "code",
        "colab": {}
      },
      "source": [
        "versioninfo()"
      ],
      "execution_count": 0,
      "outputs": []
    }
  ]
}

```

 ![SnapCrab_NoName_2026-4-15_14-11-1_No-00](https://global.discourse-cdn.com/julialang/original/3X/1/b/1b1fc5adabc9efc51dd9b331594236aab392263f.png)