ImportError when installing a package with a dependency on another package even though the required package is installed

[AlessandroPomponio]

Issue

Hello,
I'm trying out uv and I'm encountering a weird error with it.

The package pytorch-fast-transformers requires torch to be installed. Despite it being installed in the venv and appearing when doing uv pip show torch, attempting to install pytorch-fast-transformers will result in an ImportError.

Example:

uv venv
source .venv/bin/activate
uv pip install torch
uv pip install pytorch-fast-transformers

Will output the following:

error: Failed to download and build: pytorch-fast-transformers==0.4.0
  Caused by: Failed to build: pytorch-fast-transformers==0.4.0
  Caused by: Build backend failed to determine extra requires with `build_wheel()` with exit status: 1
--- stdout:

--- stderr:
Traceback (most recent call last):
  File "<string>", line 19, in <module>
ModuleNotFoundError: No module named 'torch'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<string>", line 14, in <module>
  File "/Users/alessandropomponio/Library/Caches/uv/.tmp2WMNKV/.venv/lib/python3.10/site-packages/setuptools/build_meta.py", line 325, in get_requires_for_build_wheel
    return self._get_build_requires(config_settings, requirements=['wheel'])
  File "/Users/alessandropomponio/Library/Caches/uv/.tmp2WMNKV/.venv/lib/python3.10/site-packages/setuptools/build_meta.py", line 295, in _get_build_requires
    self.run_setup()
  File "/Users/alessandropomponio/Library/Caches/uv/.tmp2WMNKV/.venv/lib/python3.10/site-packages/setuptools/build_meta.py", line 487, in run_setup
    super().run_setup(setup_script=setup_script)
  File "/Users/alessandropomponio/Library/Caches/uv/.tmp2WMNKV/.venv/lib/python3.10/site-packages/setuptools/build_meta.py", line 311, in run_setup
    exec(code, locals())
  File "<string>", line 22, in <module>
ImportError: PyTorch is required to install pytorch-fast-transformers. Please install your favorite version of PyTorch, we support 1.3.1, 1.5.0 and >=1.6
---

Note

Output with -v flag below

Disclose here

INFO Found a virtualenv through VIRTUAL_ENV at: /Users/alessandropomponio/uv-test/.venv
DEBUG Cached interpreter info for Python 3.10.12, skipping probing: .venv/bin/python
DEBUG Using Python 3.10.12 environment at .venv/bin/python
DEBUG Trying to lock if free: .venv/.lock
DEBUG Using registry request timeout of 300s
DEBUG Solving with target Python version 3.10.12
DEBUG Adding direct dependency: pytorch-fast-transformers*
TRACE Fetching metadata for pytorch-fast-transformers from https://pypi.org/simple/pytorch-fast-transformers/
TRACE cached request https://pypi.org/simple/pytorch-fast-transformers/ is storable because its response has a 'public' cache-control directive
DEBUG Found fresh response for: https://pypi.org/simple/pytorch-fast-transformers/
TRACE Received package metadata for: pytorch-fast-transformers
TRACE selecting candidate for package pytorch-fast-transformers with range Range { segments: [(Unbounded, Unbounded)] } with 8 remote versions
TRACE found candidate for package PackageName("pytorch-fast-transformers") with range Range { segments: [(Unbounded, Unbounded)] } after 0 steps: "0.4.0" version
DEBUG Searching for a compatible version of pytorch-fast-transformers (*)
TRACE selecting candidate for package pytorch-fast-transformers with range Range { segments: [(Unbounded, Unbounded)] } with 8 remote versions
TRACE found candidate for package PackageName("pytorch-fast-transformers") with range Range { segments: [(Unbounded, Unbounded)] } after 0 steps: "0.4.0" version
DEBUG Selecting: pytorch-fast-transformers==0.4.0 (pytorch-fast-transformers-0.4.0.tar.gz)
TRACE cached request https://files.pythonhosted.org/packages/ea/bc/00f597fefeab6341114c41045c1b232c38436738e0e8eac1bc9d5e9d5962/pytorch-fast-transformers-0.4.0.tar.gz is storable because its response has a 'public' cache-control directive
DEBUG Found fresh response for: https://files.pythonhosted.org/packages/ea/bc/00f597fefeab6341114c41045c1b232c38436738e0e8eac1bc9d5e9d5962/pytorch-fast-transformers-0.4.0.tar.gz
DEBUG Preparing metadata for: pytorch-fast-transformers==0.4.0
DEBUG No static `PKG-INFO` available for: pytorch-fast-transformers==0.4.0 (DynamicPkgInfo(UnsupportedMetadataVersion("2.1")))
DEBUG No static `pyproject.toml` available for: pytorch-fast-transformers==0.4.0 (MissingPyprojectToml)
DEBUG Solving with target Python version 3.10.12
DEBUG Adding direct dependency: setuptools>=40.8.0
TRACE Fetching metadata for setuptools from https://pypi.org/simple/setuptools/
TRACE cached request https://pypi.org/simple/setuptools/ is storable because its response has a 'public' cache-control directive
DEBUG Found fresh response for: https://pypi.org/simple/setuptools/
TRACE Received package metadata for: setuptools
TRACE selecting candidate for package setuptools with range Range { segments: [(Included("40.8.0"), Unbounded)] } with 550 remote versions
TRACE found candidate for package PackageName("setuptools") with range Range { segments: [(Included("40.8.0"), Unbounded)] } after 0 steps: "69.2.0" version
DEBUG Searching for a compatible version of setuptools (>=40.8.0)
TRACE selecting candidate for package setuptools with range Range { segments: [(Included("40.8.0"), Unbounded)] } with 550 remote versions
TRACE found candidate for package PackageName("setuptools") with range Range { segments: [(Included("40.8.0"), Unbounded)] } after 0 steps: "69.2.0" version
DEBUG Selecting: setuptools==69.2.0 (setuptools-69.2.0-py3-none-any.whl)
TRACE cached request https://files.pythonhosted.org/packages/92/e1/1c8bb3420105e70bdf357d57dd5567202b4ef8d27f810e98bb962d950834/setuptools-69.2.0-py3-none-any.whl.metadata is storable because its response has a 'public' cache-control directive
DEBUG Found fresh response for: https://files.pythonhosted.org/packages/92/e1/1c8bb3420105e70bdf357d57dd5567202b4ef8d27f810e98bb962d950834/setuptools-69.2.0-py3-none-any.whl.metadata
TRACE Received built distribution metadata for: setuptools==69.2.0
DEBUG Installing in setuptools==69.2.0 in /Users/alessandropomponio/Library/Caches/uv/.tmpbwwP79/.venv
DEBUG Requirement already cached: setuptools==69.2.0
DEBUG Installing build requirement: setuptools==69.2.0
DEBUG Calling `setuptools.build_meta:__legacy__.get_requires_for_build_wheel()`
error: Failed to download and build: pytorch-fast-transformers==0.4.0
  Caused by: Failed to build: pytorch-fast-transformers==0.4.0
  Caused by: Build backend failed to determine extra requires with `build_wheel()` with exit status: 1
--- stdout:

--- stderr:
Traceback (most recent call last):
  File "<string>", line 19, in <module>
ModuleNotFoundError: No module named 'torch'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<string>", line 14, in <module>
  File "/Users/alessandropomponio/Library/Caches/uv/.tmpbwwP79/.venv/lib/python3.10/site-packages/setuptools/build_meta.py", line 325, in get_requires_for_build_wheel
    return self._get_build_requires(config_settings, requirements=['wheel'])
  File "/Users/alessandropomponio/Library/Caches/uv/.tmpbwwP79/.venv/lib/python3.10/site-packages/setuptools/build_meta.py", line 295, in _get_build_requires
    self.run_setup()
  File "/Users/alessandropomponio/Library/Caches/uv/.tmpbwwP79/.venv/lib/python3.10/site-packages/setuptools/build_meta.py", line 487, in run_setup
    super().run_setup(setup_script=setup_script)
  File "/Users/alessandropomponio/Library/Caches/uv/.tmpbwwP79/.venv/lib/python3.10/site-packages/setuptools/build_meta.py", line 311, in run_setup
    exec(code, locals())
  File "<string>", line 22, in <module>
ImportError: PyTorch is required to install pytorch-fast-transformers. Please install your favorite version of PyTorch, we support 1.3.1, 1.5.0 and >=1.6
---

With the following, however, we can see that torch is correctly installed and available:

uv pip show torch
Name: torch
Version: 2.2.2
Location: /Users/alessandropomponio/uv-test/.venv/lib/python3.10/site-packages
Requires: filelock, fsspec, jinja2, networkx, sympy, typing-extensions
Required-by:

Running import torch from an interactive python session also works.

Details

System: MacOS
Python Version: Python 3.10.12
UV Version: uv 0.1.31

[AlessandroPomponio]

The fact that setuptools gets installed in a temporary venv despite being available in the currently active venv makes me think the installation process is working in isolation and ends up causing the error I encountered

[charliermarsh]

I believe you need to run with --no-build-isolation since pytorch-fast-transformers depends on Torch, but doesn't include it in its build dependencies.

pip also fails to install this package with --use-pep517, which will eventually be the default in pip (and is the default in uv today):

❯ pip install pytorch-fast-transformers --use-pep517
Collecting pytorch-fast-transformers
  Downloading pytorch-fast-transformers-0.4.0.tar.gz (93 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 93.6/93.6 kB 4.2 MB/s eta 0:00:00
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  error: subprocess-exited-with-error

  × Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [26 lines of output]
      Traceback (most recent call last):
        File "<string>", line 19, in <module>
      ModuleNotFoundError: No module named 'torch'

      The above exception was the direct cause of the following exception:

      Traceback (most recent call last):
        File "/Users/crmarsh/.local/share/rtx/installs/python/3.12.1/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
          main()
        File "/Users/crmarsh/.local/share/rtx/installs/python/3.12.1/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 335, in main
          json_out['return_val'] = hook(**hook_input['kwargs'])
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/Users/crmarsh/.local/share/rtx/installs/python/3.12.1/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 118, in get_requires_for_build_wheel
          return hook(config_settings)
                 ^^^^^^^^^^^^^^^^^^^^^
        File "/private/var/folders/nt/6gf2v7_s3k13zq_t3944rwz40000gn/T/pip-build-env-wn0uzfrt/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 325, in get_requires_for_build_wheel
          return self._get_build_requires(config_settings, requirements=['wheel'])
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/private/var/folders/nt/6gf2v7_s3k13zq_t3944rwz40000gn/T/pip-build-env-wn0uzfrt/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 295, in _get_build_requires
          self.run_setup()
        File "/private/var/folders/nt/6gf2v7_s3k13zq_t3944rwz40000gn/T/pip-build-env-wn0uzfrt/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 487, in run_setup
          super().run_setup(setup_script=setup_script)
        File "/private/var/folders/nt/6gf2v7_s3k13zq_t3944rwz40000gn/T/pip-build-env-wn0uzfrt/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 311, in run_setup
          exec(code, locals())
        File "<string>", line 22, in <module>
      ImportError: PyTorch is required to install pytorch-fast-transformers. Please install your favorite version of PyTorch, we support 1.3.1, 1.5.0 and >=1.6
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: subprocess-exited-with-error

× Getting requirements to build wheel did not run successfully.
│ exit code: 1
╰─> See above for output.

note: This error originates from a subprocess, and is likely not a problem with pip.

Try uv pip install pytorch-fast-transformers --no-build-isolation.

[charliermarsh]

(Added a note here: #2252)

[AlessandroPomponio]

Thank you very much Charlie! That was it!
Have a great day!

[charliermarsh]

No prob :)