How to create a Python executable with nix flake

Question

I have a directory with two files, main.py and flake.nix.

flake.nix:

{
  description = "virtual environment with python and streamlit";
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  inputs.flake-utils.url = "github:numtide/flake-utils";

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        python = pkgs.python311;
        python_packages = python.withPackages(ps: with ps;[
          ipython
          matplotlib
          pandas

        ]);


        myDevTools = [
          python_packages
        ];
      in {
        devShells.default = pkgs.mkShell {
          buildInputs = myDevTools;
        };
      });
}

What should I use in flake.nix in order to create an executable that is equivalent to the following?

    python main.py

I want to create the executable with the command

    nix build

in the shell (it means with the necessary packages installed)

I have added apps in my file:

{
  description = "virtual environment with python and streamlit";
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  inputs.flake-utils.url = "github:numtide/flake-utils";

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        python = pkgs.python311;
        f = ps: with ps;[
          ipython
          matplotlib
          pandas
        ];
        pip_python_packages = python.withPackages(f);

        myDevTools = [
          pip_python_packages
          pkgs.streamlit
        ];
        outputName = builtins.attrNames self.outputs self.outputs;
      in {
        devShells.default = pkgs.mkShell {
          buildInputs = myDevTools;
        };

        packages.default = pkgs.poetry2nix.mkPoetryApplication {
          projectDir = self;
        };
        apps.default = {
          program = "${python}/bin/python";
          args = [ "main.py" ];
          src = "./.";
          type = "app";
      };

      });
}

But nix runs only to open the python interpreter.

Furthermore, I enter this line

    nix/store/cxsw4x1189ppmsydhwsmssr0x65nygj7-python3-3.11.4/bin/python ./main.py

in my shell

because ${python} = cxsw4x1189ppmsydhwsmssr0x65nygj7-python3-3.11.4/bin/python

And it didn't work:

ModuleNotFoundError: No module named 'pandas'

I changed my file like this:

{
  description = "virtual environment with python and streamlit";
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  inputs.flake-utils.url = "github:numtide/flake-utils";

  outputs = { self, nixpkgs, flake-utils }: flake-utils.lib.eachDefaultSystem (system:
    let
      pkgs = nixpkgs.legacyPackages.${system};
      python = pkgs.python311;
      f = ps: with ps;[
        ipython
        matplotlib
        pandas
      ];
      pip_python_packages = python.withPackages(f);

      myDevTools = [
        pip_python_packages
        pkgs.streamlit
      ];
      outputName = builtins.attrNames self.outputs self.outputs;
    in {
      devShells.default = pkgs.mkShell {
        buildInputs = myDevTools;
      };

      packages.default = pkgs.poetry2nix.mkPoetryApplication {
        projectDir = self;
      };

      apps.default = flake-utils.lib.mkApp {
        program = "${pip_python_packages}/bin/python";
        args = [ "${self}/main.py" ];
      };
    });
}

But I have this error now after running nix run:

error: … while evaluating the attribute 'pkgs.buildPythonPackage'

     at /nix/store/s1z7nb9n6r5n0r34fabp6yybwkbr8mjk-source/pkgs/development/interpreters/python/passthrufun.nix:87:5:

       86|     withPackages = import ./with-packages.nix { inherit buildEnv pythonPackages;};
       87|     pkgs = pythonPackages;
         |     ^
       88|     interpreter = "${self}/bin/${executable}";

   … while calling the 'mapAttrs' builtin

     at /nix/store/s1z7nb9n6r5n0r34fabp6yybwkbr8mjk-source/pkgs/development/interpreters/python/passthrufun.nix:31:8:

       30|           value;
       31|     in lib.mapAttrs func items;
         |        ^
       32|   in ensurePythonModules (callPackage

   (stack trace truncated; use '--show-trace' to show the full trace)

   error: getting status of '/nix/store/c274sjvcr30c80429v9kpn4n2q0ic6n9-source/poetry.lock': No

such file or directory