Pip Install from Pypi Works, But from Testpypi Fails (Cannot Find Requirements)

Pip install from pypi works, but from testpypi fails (cannot find requirements)

Update

PyPI has upgraded its site. According to the docs, the new advice is:

pip install --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple poirot

• --index-url points to your package on TestPyPI.
• --extra-index-url points to dependencies on PyPI.
• poirot is your package.

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Out-dated

Try pip install --extra-index-url https://testpypi.python.org/pypi poirot.

See also a reference post.

Can't install my own PyPi package: requirements can't be satisfied

You can have only one index but you can have as many extra indices as you wish. Add the main PyPI as an extra index:

pip install -i https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ my_package_name

First pip looks into the index and then scan extra indices until it finds the package.

Numpy install requirement on package fails on pip install from PyPI but not from .whl

If you look at your error message, you can see

Downloading ... mathsom-0.1.1-py3-none-any.whl

So it is also using a whl file. However, the way numpy is installed differs. In your error message, it is clear that numpy is trying to compile from source, which is not suprising, since you set the index to https://test.pypi.org/simple/ and there is only source distributions of numpy under that index. If you allow that the dependencies can be pulled from pypi, by setting test.pypi as an extra-index with --extra-index-url then everything works (tested in a fresh conda env created with the command you have provided):

pip install --extra-index-url https://test.pypi.org/simple/ mathsom
Looking in indexes: https://pypi.org/simple, https://test.pypi.org/simple/
Collecting mathsom
  Downloading https://test-files.pythonhosted.org/packages/4b/b3/76e6bbaa6c1da9f6f032e114af7f5724077154a28b5fc7069330185f2bc8/mathsom-0.1.1-py3-none-any.whl (18 kB)
Collecting scipy
  Downloading scipy-1.5.4-cp36-cp36m-win_amd64.whl (31.2 MB)
     |████████████████████████████████| 31.2 MB 393 kB/s
Collecting numpy
  Downloading numpy-1.19.5-cp36-cp36m-win_amd64.whl (13.2 MB)
     |████████████████████████████████| 13.2 MB ...
Installing collected packages: numpy, scipy, mathsom
Successfully installed mathsom-0.1.1 numpy-1.19.5 scipy-1.5.4

Python Pip: pip install cannot find a version that satisfies a requirement - despite present in pyproject.toml

Main Error

TLDR; Pip tries to resolve dependencies with TestPypi, but they are in another index (Pypi). Workarounds at end of answer.

The fact that I am publishing to TestPypi is the reason this has happened. I will explain why what I did made this error appear, and then I will show how you, from the future, may solve this.

Difference between Pypi and TestPypi

Pypi is the Python Package Index. It's a giant index of Python packages one may install from with pip install.
TestPypi is the Python Package Index designated for testing and publishing without touching the real Package Index. It can be useful in times when learning how to publish a package. The main difference is that it is a completely separate repository. Therefore, what's on TestPypi may not be exactly what's on Pypi.
My research was limited, so if I confused anyone, the main difference is that they are two different Package Indexes. One was made for testing purposes.

I published my package to TestPypi and set my pip install to install from that repository. Not Pypi, but TestPypi.

Why dependency resolution failed

When I defined my project's dependencies, I defined them based off of their Pypi presences. Most dependencies are present in Pypi. Not TestPypi. This meant that when I asked for my package from TestPypi, pip only looked at TestPypi, and the pip installer workflow fell out to a pattern like this:

0.5. Set fetching repository to TestPypi and Not Pypi.

1. Pull package from TestPypi
2. Install and examine dependencies
3. Find first dependency (e.g. Beautifulsoup4)
4. Pull dependency from TestPypi
5. Successfully install Beautifulsoup4
   -. This is because beautifulsoup4 is actually present in the TestPypi.
6. Move on to another dependency (e.g. rich)
7. Fail to pull from TestPypi
   -. Rich is not present in TestPypi.
8. Return dependency not found.

Why some dependencies oddly worked

As you see in workflow step 5., the beautifulsoup4 package was found on the TestPypi. (Someone had put it up there).
image to TestPypi page with beautifulsoup4
However, as you see in step 7., Rich is not found on the TestPypi index. This issue occurs because I set my repoistiroy to install from TestPypi because my that is where my package was held. This caused pip to use TestPypi. for every single dependency as well.

How I got around it.

I got around it by using TestPypi to verify accurate build artifact publishing, and then I jumped to Normal Pypi to test installation and dependency installation.

Workarounds

Install from TestPypi

python3 -m pip install -i https://test.pypi.org/simple/ <package name>

Install from Pypi (by default)

python3 -m pip install <package name>

Install package from TestPypi but dependencies from Pypi

The Python Docs explains this very well.

If you want to allow pip to also download packages from PyPI, you can specify --extra-index-url to point to PyPI. This is useful when the package you’re testing has dependencies:

python3 -m pip install --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ your-package

module on test.pypi can't install dependencies, even though they exist

-i URL, or --index-url URL means "use URL for installing packages from exclusively". By passing -i https://test.pypi.org/simple/, you thus prohibit searching and downloading packages from PyPI (https://pypi.org/simple). To use both indexes, use --extra-index-url:

$ python -m pip install --extra-index-url https://test.pypi.org/simple/ sameWidther

pip install producing Could not find a version that satisfies the requirement

If you use --index-url pip will no longer install from "proper PyPI", but only from "test PyPI". If instead you use --extra-index-url, it will install from both:

pip install --extra-index-url https://test.pypi.org/simple/ package_name_here

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