How to make pip fail early when one of the requested requirements does not exist?

Question

Minimal example:

pip install tensorflow==2.9.1 non-existing==1.2.3

Defaulting to user installation because normal site-packages is not writeable
Looking in indexes: https://pypi.org/simple, https://pypi.ngc.nvidia.com
Collecting tensorflow==2.9.1
  Downloading tensorflow-2.9.1-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (511.7 MB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 511.7/511.7 MB 7.6 MB/s eta 0:00:00
ERROR: Could not find a version that satisfies the requirement non-existing==1.2.3 (from versions: none)
ERROR: No matching distribution found for non-existing==1.2.3

So pip downloads the (rather huge) TensorFlow first, only to then tell me that non-existing does not exist.

Is there a way to make it fail earlier, i.e., print the error and quit before downloading?

Answer 1

I'm afraid there's no straightforward way of handling it. I ended up writing a simple bash script where I check the availability of packages using pip's index command:

check_packages_availability () {
  while IFS= read -r line || [ -n "$line" ]; do
      package_name="${line%%=*}"
      package_version="${line#*==}"

      if ! pip index versions $package_name | grep "$package_version"; then
        echo "package $line not found"
        exit -1
      fi
  done < requirements.txt
}

if ! check_packages_availability; then
  pip install -r requirements.txt
fi

This is a hacky solution but may work. For every package in requirements.txt this script tries to retrieve information about it and match the specified version. If everything's alright it starts installing them.

---

Or you can use poetry, it handles resolving dependencies for you, for example:

pyproject.toml

[tool.poetry]
name = "test_missing_packages"
version = "0.1.0"
description = ""
authors = ["funnydman"]

[tool.poetry.dependencies]
python = "^3.10"
tensorflow = "2.9.1"
non-existing = "1.2.3"

[build-system]
requires = ["poetry-core>=1.0.0"]
build-backend = "poetry.core.masonry.api"

At the resolving stage it throws exception without installing/downloading packages:

Updating dependencies
Resolving dependencies... (0.2s)

SolverProblemError
    
Because test-missing-packages depends on non-existing (1.2.3) which doesn't match any versions, version solving failed.