# How to Fix pyenv's "No module named '_lzma'" Error


A pyenv-installed Python that raises this error is missing its lzma extension module:

```
ModuleNotFoundError: No module named '_lzma'
```

The same problem also shows up as a warning when a library touches a `.xz` archive:

```
UserWarning: Could not import the lzma module. Your installed Python is incomplete.
```

pyenv compiles Python from source. The standard library's `lzma` module is a C extension that links against the external `xz` (liblzma) library, and that library has to be present when the interpreter is built. If it is missing, [pyenv](https://pydevtools.com/handbook/reference/pyenv.md) still finishes the build and prints only a warning, so the broken interpreter looks fine until something imports `lzma`.

## Confirm the module is missing

Run the import directly against the affected interpreter:

```console
$ python -c "import lzma"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named '_lzma'
```

A complete interpreter prints nothing and exits zero. The traceback confirms the build omitted `_lzma`.

## Why installing xz alone does not fix it

`_lzma` is decided when pyenv compiles the interpreter. Installing `xz` afterward puts the library on the system, but the already-built Python was linked without it and does not pick it up. The interpreter has to be recompiled against the now-present library, which means uninstalling and reinstalling that version.

## Rebuild the interpreter with xz present

Install the `xz` development files, then reinstall the affected Python version so pyenv recompiles against them.

Install `xz` with [Homebrew](https://pydevtools.com/handbook/reference/homebrew.md):

```bash
brew install xz
```

Reinstall the affected version (substitute your own):

```bash
pyenv uninstall 3.12.0
pyenv install 3.12.0
```
Install the liblzma development package for your distribution:

```bash
# Debian / Ubuntu
sudo apt install liblzma-dev

# Fedora
sudo dnf install xz-devel
```

Reinstall the affected version (substitute your own):

```bash
pyenv uninstall 3.12.0
pyenv install 3.12.0
```
Confirm the rebuilt interpreter imports `lzma`:

```console
$ python -c "import lzma"
```

No output means the module is back.

The same build-dependency trap hits other extension modules: `readline` (line editing), `sqlite3`, `bz2`, and `ssl` all go silently missing when their libraries are absent at compile time. pyenv's [suggested build environment](https://github.com/pyenv/pyenv/wiki#suggested-build-environment) lists every dependency to install before building.

## Point the build at xz when it still fails

If `pyenv install` still omits `_lzma` after installing `xz` on macOS, Homebrew may have placed the library where the compiler does not look by default. Export the paths so the build finds it, then reinstall:

```bash
export LDFLAGS="-L$(brew --prefix xz)/lib"
export CPPFLAGS="-I$(brew --prefix xz)/include"
export PKG_CONFIG_PATH="$(brew --prefix xz)/lib/pkgconfig"
pyenv install 3.12.0
```

`brew --prefix xz` expands to the installed location (`/opt/homebrew/opt/xz` on Apple Silicon, `/usr/local/opt/xz` on Intel), so the same commands work on both architectures.

## Skip source compilation with uv

The failure exists because pyenv builds Python from source and depends on the right system libraries being present. [uv](https://pydevtools.com/handbook/reference/uv.md) removes that step. It downloads prebuilt [python-build-standalone](https://github.com/astral-sh/python-build-standalone) interpreters that already include `lzma`, `sqlite3`, `readline`, and the other extension modules, so there is nothing to compile and nothing to get wrong:

```console
$ uv python install 3.12
Installed Python 3.12.7 in 646ms
```

The resulting interpreter is complete on the first try. See [how to install Python with uv](https://pydevtools.com/handbook/how-to/how-to-install-python-with-uv.md) for the full command set, and [how to switch from pyenv to uv](https://pydevtools.com/handbook/how-to/how-to-switch-from-pyenv-to-uv-for-managing-python-versions.md) to move version management over entirely.

> [!NOTE]
> pyenv proper runs only on macOS and Linux. This build failure is a source-compilation issue that does not apply to [pyenv-win](https://github.com/pyenv-win/pyenv-win), which installs official prebuilt Python binaries on Windows.

## Learn More

- [How to install Python with uv](https://pydevtools.com/handbook/how-to/how-to-install-python-with-uv.md)
- [How to switch from pyenv to uv for managing Python versions](https://pydevtools.com/handbook/how-to/how-to-switch-from-pyenv-to-uv-for-managing-python-versions.md)
- [How do pyenv and uv compare for Python interpreter management?](https://pydevtools.com/handbook/explanation/how-do-pyenv-and-uv-compare-for-python-interpreter-management.md)
- [pyenv Common build problems](https://github.com/pyenv/pyenv/wiki/Common-build-problems)