creates a working impure python env in nixos. replace <packages> with the packages you want.

python-pip-env-default.nix

with import <nixpkgs> {};
with pkgs.python27Packages;

stdenv.mkDerivation {
  name = "impurePythonEnv";
  buildInputs = [
    automake
    autoconf
    gcc-arm-embedded-7
    # these packages are required for virtualenv and pip to work:
    #
    python3
    python3Packages.virtualenv
    python3Packages.pip
    python3Packages.numpy
    python3Packages.setuptools
    python3Packages.pandas
    
    taglib
    openssl
    git
    stdenv
    zlib ];
  src = null;
  shellHook = ''
    # set SOURCE_DATE_EPOCH so that we can use python wheels
    SOURCE_DATE_EPOCH=$(date +%s)
    virtualenv --no-setuptools .venv
    export PATH=$PWD/.venv/bin:$PATH
    # the following is required to build micro_ecc_lib_nrf52.a in the SDK
    export GNU_INSTALL_ROOT="${gcc-arm-embedded-7}/bin/"
    export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:${stdenv.cc.cc.lib}/lib/libstdc++.so.6"
    pip install <packages>
    
    unset CC
  '';
}