TL;DR: your fastparquet is too old for your pandas. pandas removed RangeIndex from pandas.core.index, so upgrade fastparquet to a compatible release, or pin an older pandas.

## The error
```text
ImportError: cannot import name RangeIndex
```

## Fix it
1. Upgrade fastparquet:
   ```
   pip install -U fastparquet
   ```
   Expected: installs a release that imports RangeIndex from the right place.
2. Verify:
   ```
   python -c "import fastparquet; print('ok')"
   ```
   Expected: imports cleanly.
3. Workaround if you cannot upgrade fastparquet: pin pandas to a version that still has the old path:
   ```
   pip install "pandas<1.0"
   ```
   Expected: the old import path works again.

## When this applies
Use this when `import fastparquet` raises the RangeIndex error with a modern pandas.

## When it does not apply
If your own code imports RangeIndex from pandas.core.index, use pandas.RangeIndex instead. If fastparquet is current, reinstall it.

## Compatibility
Old fastparquet with pandas 1.0+. pandas.RangeIndex is the stable public path on all pandas versions.

## Root cause
pandas reorganized its internals and removed the pandas.core.index alias for RangeIndex. fastparquet imported the internal path, so the removal broke it at import time.

## Edge cases
Pinning ancient pandas breaks most of the modern stack; upgrading fastparquet is strongly preferred. The same pandas-internal cleanup broke other old libraries the same way.