{ pkgs, pythonPackages }:

with builtins;

with pythonPackages;

with { inherit (pkgs) lib; };

let removeNulls = lib.filterAttrs (n: v: v != null);
    srcHelper = url: sha256: curlOpts: name:
      assert url != null;
      assert sha256 != null;
      pkgs.fetchurl (removeNulls { inherit url sha256 name curlOpts; });

    mkPython =
      { packageName            # < A package name.
      , version                # < A package version.
      , srcURL          ? null # < A url to download from.
      , srcSHA          ? null # < A SHA256 checksum for the download.
      , srcName         ? null # < A name for the downloaded file.
      , srcCurlOpts     ? null # < A curl options for the download.
      , src             ? null # < A source to use (overrides other options).
      , buildDeps       ? []   # < Build dependencies to add.
      , propDeps        ? []   # < Propagated dependencies to add.
      , nativeBuildDeps ? []   # < Native build dependencies to add.
      , nativePropDeps  ? []   # < Native propagated dependencies to add.
      # The following attributes are equivalent to those in meta:
      , homepage        ? null # < A homepage of the project.
      , description     ? null # < A description.
      , longDescription ? null # < A longer description.
      , maintainers     ? null # < A list of maintainers.
      , license         ? null # < A license.
      , platforms       ? null # < A list of supported platforms.
      , ... # Any other options will be passed to buildPythonPackage directly
      } @ args:

      buildPythonPackage (removeNulls ({
        name = "${packageName}-${version}";

        src = if isNull src
              then srcHelper srcURL srcSHA srcCurlOpts srcName
              else src;

        buildInputs           = buildDeps;
        propagatedBuildInputs = propDeps;

        nativeBuildInputs           = nativeBuildDeps;
        propagatedNativeBuildInputs = nativePropDeps;

        meta = removeNulls {
          inherit homepage description longDescription
                  license maintainers platforms;
        };
      } // args));
   isNonEmptyString = x: stringLength x > 0;
   strHead = x: (assert isNonEmptyString x; substring 0 1 x);
   pypiURL = name: version:
     assert isNonEmptyString name;
     assert isNonEmptyString version;
     "mirror://pypi/${strHead name}/${name}/${name}-${version}.tar.gz";

in pythonPackages // (rec {
  # bobbuilder = pkgs.callPackage ./bobbuilder {};

# No longer used, Theano was finally added to nix main channel
#  theano-deep = mkPython (rec {
#    packageName  = "theano-deep";
#    version      = "0.8.2";
#    srcURL       = pypiURL "Theano" version;
#    srcSHA       = "0c49mz3bg57vigkyfz3yd6302587hsikhvgkh7w7ny0sxpvwhqvl";
#    propDeps     = with pkgs; [ six scipy ];
#    homepage     = http://deeplearning.net/software/theano/;
#    description  = "Optimizing compiler for evaluating mathematical expressions on CPUs and GPUs.";
#    license      = null;#lib.licenses.bsd;
#    maintainers  = null;
#    platforms    = with lib.platforms; all;
#
#  });

  panda3d = mkPython (rec {