How to Fix Command Errored Out With Exit Status 1 in Python

“Command errored out with exit status 1” means a package’s build step crashed. Newer pip calls it error: subprocess-exited-with-error. The real cause is in the output block above that line; read it, then try:

python -m pip install --upgrade pip setuptools wheel
python -m pip install --only-binary :all: <package>

I ran everything below on October 12, 2026 in scratch venvs on Python 3.12.5 and 3.14.8, using a tiny local package, invoice_tool, whose setup.py needs Cython.

What does command errored out with exit status 1 mean in pip?

Exit status 1 means a child process failed. Older pip printed ERROR: Command errored out with exit status 1; current pip prints a framed subprocess-exited-with-error block instead. Here’s my package with pip 26.2.1 (internal frames trimmed to ...):

from setuptools import setup
from Cython.Build import cythonize   # Cython is needed just to build this package

setup(
    name="invoice-tool",
    version="1.0.0",
    ext_modules=cythonize("totals.pyx"),
)

Output:

Processing .\invoice_tool
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'error'
  error: subprocess-exited-with-error
  
  × Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [21 lines of output]
      Traceback (most recent call last):
        ...
        File "<string>", line 2, in <module>
      ModuleNotFoundError: No module named 'Cython'
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed to build 'file:///C:/pyguides/exitstatus1/invoice_tool' when getting requirements to build wheel

Not sure which interpreter owns the pip you ran? Running multiple Python versions side by side shows how to call each one.

How do I find the real error in pip’s output?

Skip the bottom summary and read the last line before [end of output]. The step name tells you where it broke:

Step that failed	Final error line	Usual cause
Getting requirements to build wheel	subprocess-exited-with-error	setup.py crashed, often a missing import
Preparing metadata	metadata-generation-failed	No wheel for your Python, so pip tried a source build
Building wheel	failed-wheel-build-for-install	No C/C++ compiler or missing system library

A missing module at import time is a different problem, covered in fixing ModuleNotFoundError after pip install.

Upgrade pip, setuptools and wheel in your virtual environment

Old build tools are a common cause, so upgrade them inside your venv:

sv\Scripts\python -m pip --version
sv\Scripts\python -m pip install -q --upgrade pip setuptools wheel
sv\Scripts\python -m pip --version

I ran the failing install in that upgraded venv, so the upgrade alone didn’t fix the Cython error. It’s still the first step in guides like installing Matplotlib in Python.

Fix missing build dependencies and Microsoft Visual C++ 14.0 errors

pip builds in an isolated environment holding only what the package declares. Install Cython yourself and pass --no-build-isolation; pip’s docs say that needs the build dependencies preinstalled:

sv\Scripts\python -m pip install -q cython
sv\Scripts\python -m pip install --no-build-isolation .\invoice_tool

That’s progress. On Windows, install Microsoft C++ Build Tools with the “Desktop development with C++” workload, then reopen the terminal so it sees the new environment variables.

Why is pip building from source? Check wheels for your Python version

pip normally downloads prebuilt wheels. Trouble starts when a pinned version has no wheel for your Python, like numpy 1.26.4 on Python 3.14:

--only-binary :all: refuses source builds, so it shows which versions actually have wheels:

py314\Scripts\python -m pip install --dry-run --only-binary :all: numpy==1.26.4
py314\Scripts\python -m pip install --dry-run --only-binary :all: numpy

Output:

C:\pyguides\exitstatus1>py314\Scripts\python -m pip install --dry-run --only-binary :all: numpy==1.26.4 
ERROR: Ignored the following yanked versions: 2.4.0
ERROR: Could not find a version that satisfies the requirement numpy==1.26.4 (from versions: 2.3.2, 2.3.3, 2.3.4, 2.3.5, 2.4.0rc1, 2.4.1, 2.4.2, 2.4.3, 2.4.4, 2.4.5, 2.4.6, 2.5.0rc1, 2.5.0, 2.5.1, 2.5.2, 2.5.3, 2.5.4)
ERROR: No matching distribution found for numpy==1.26.4

C:\pyguides\exitstatus1>py314\Scripts\python -m pip install --dry-run --only-binary :all: numpy 
Collecting numpy
  Using cached numpy-2.5.4-cp314-cp314-win_amd64.whl.metadata (6.6 kB)
Would install numpy-2.5.4

The fix is to move to numpy 2.5.4 or keep the old pin on an older Python; installing a specific package version with pip shows how.

A few more troubleshooting reads from the site:

• Fix UnboundLocalError in Python
• Is Python a compiled language?
• Best Python libraries for data science
• PyCharm vs VS Code for Python

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