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Code Execution Ordering Dependence #9407

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#9411
Closed
Code Execution Ordering Dependence#9407
#9411
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documentationImprovements or additions to documentation
@TateStaples

Description

@TateStaples
TateStaples
opened on Apr 27, 2026

Describe the bug

I was writing code with a _cache variable and I noticed that this leads to the code behaving non-deterministically depending on your chosen execution order.

I understand if this is problematic to try to solve with dependency analysis but was hoping it could at least end up as a warning somewhere so this gotcha doesn't happen to anyone else

Will you submit a PR?

  • Yes

Environment

Details 
{
  "marimo": "0.23.2",
  "editable": false,
  "location": "/Users/tatestaples/Code/Explorations/.venv/lib/python3.13/site-packages/marimo",
  "OS": "Darwin",
  "OS Version": "24.1.0",
  "Processor": "arm",
  "Python Version": "3.13.11",
  "Locale": "C/en_US",
  "Binaries": {
    "Browser": "147.0.7727.103",
    "Node": "v25.9.0",
    "uv": "0.10.10 (Homebrew 2026-03-13)"
  },
  "Dependencies": {
    "click": "8.3.1",
    "docutils": "0.22.4",
    "itsdangerous": "2.2.0",
    "jedi": "0.19.2",
    "markdown": "3.10.2",
    "narwhals": "2.18.0",
    "packaging": "26.0",
    "psutil": "7.2.2",
    "pygments": "2.19.2",
    "pymdown-extensions": "10.21",
    "pyyaml": "6.0.3",
    "starlette": "1.0.0",
    "tomlkit": "0.14.0",
    "typing-extensions": "4.15.0",
    "uvicorn": "0.42.0",
    "websockets": "16.0"
  },
  "Optional Dependencies": {
    "altair": "6.0.0",
    "anywidget": "0.9.21",
    "duckdb": "1.5.1",
    "loro": "1.10.3",
    "nbformat": "5.10.4",
    "openai": "2.29.0",
    "pandas": "3.0.1",
    "polars": "1.39.3",
    "pyarrow": "23.0.1",
    "ruff": "0.15.7",
    "sqlglot": "30.0.3"
  },
  "Experimental Flags": {
    "rtc_v2": false
  }
}

Code to reproduce

# /// script
# requires-python = ">=3.12"
# dependencies = [
#     "marimo>=0.20.2",
# ]
# ///

import marimo

__generated_with = "0.23.2"
app = marimo.App(width="medium")


@app.cell
def _():
    _cache = dict()
    def square(x):
        if x in _cache:
            print("Cache Hit")
            return _cache[x] + 1
        res = x*x
        print("Cache Miss")
        _cache[x] = res
        return res

    return (square,)


@app.cell(hide_code=True)
def _(square):
    square(5)
    return


@app.cell
def _(square):
    square(5)
    return


if __name__ == "__main__":
    app.run()

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