# Notebooks, files, and what persists

The single most useful thing to know about EugoIDE: not everything you write to disk stays there.

## The rule

Files in the **workspace tree**, which is what the file browser shows, persist between sessions.
Everything else is session-local and disappears when the session ends.

```python
df.to_parquet("/workspace/results/output.parquet")   # persists
df.to_parquet("/tmp/output.parquet")                 # gone on restart
```

## Three storage locations, three purposes

**Workspace storage.** Notebooks, scripts, small reference data. Visible to your session. Persists.

**Object storage.** Large inputs and outputs. Reachable by every [compute node](/glossary/compute-node) in parallel, which
makes it the right place for anything workers read.

**Session-local (`/tmp`).** Scratch space within one session. Fast, ephemeral, and invisible to the
[cluster](/glossary/cluster).

:::warning A path that works in your notebook may not work in a task
Your session can read [workspace](/glossary/workspace) storage. A worker on a compute node generally cannot. If a task needs
data, that data belongs in [object storage](/glossary/object-storage).
:::

This is the error that produces a confusing `FileNotFoundError` inside a task while the same path
reads fine in the notebook cell above it.

## Organizing a workspace

A layout that holds up:

```
/workspace/
├── notebooks/     exploratory work
├── src/           reusable modules, imported by notebooks
├── data/          small reference files only
└── results/       local outputs worth keeping
```

Large inputs and outputs go to object storage, not into `data/`.

## Notebooks are not the only option

Long-lived logic belongs in a `.py` module under `src/`, imported by the notebook. Notebooks are for
exploration and narrative; modules are for code you will reuse or test.

```python
import sys
sys.path.insert(0, "/workspace/src")
from pipeline import transform
```

## Version control

There is no automatic history. If work matters, commit it. A terminal is available, and `git` works
as usual against your workspace tree.

## Before you close a session

Check for anything written outside the workspace tree. Once the session ends, it is not recoverable.

---

Source: https://university.eugo.io/lesson/eugoide-essentials/notebooks-and-files