Getting ready

The old way to manage virtual environments was with the venv tool. To install it, use the command sudo apt install python3-venv.

To manage virtual environments in a modern way, the pipenv module (https://docs.pipenv.org/) was developed; it automatically creates and manages virtual environments for projects, as well as adding and removing packages from Pipfile when you install/uninstall packages. It can be installed using pip install pipenv.

Pipfile is an alternative to requirements.txt, which is used to specify exact versions of modules to include in a program. Pipfile actually comprises two separate files: Pipfile and (optionally) Pipfile.lock. Pipfile is simply a listing of the source location of imported modules, the module names themselves (defaulting to the most recent version), and any development packages that are required. pipfile.py, below, is an example of a Pipfile from the Pipenv site (https://docs.pipenv.org/basics/#example-pipfile-pipfile-lock):

[[source]]
url = "https://pypi.python.org/simple"
verify_ssl = true
name = "pypi"

[packages]
requests = "*"


[dev-packages]
pytest = "*"

Pipfile.lock takes the Pipfile and sets actual version numbers to all the packages, as well as identifying specific hashes for those files. Hashed values are beneficial to minimize security risks; that is, if a particular module version has a vulnerability, its hash value allows it to be easily identified, rather than having to search by version name or some other method. pipfile_lock.py, below, is an example of a Pipfile.lock file from the Pipenv site (https://docs.pipenv.org/basics/#example-pipfile-pipfile-lock):

{
  "_meta": {
    "hash": {
      "sha256": "8d14434df45e0ef884d6c3f6e8048ba72335637a8631cc44792f52fd20b6f97a"
    },
    "host-environment-markers": {
      "implementation_name": "cpython",
      "implementation_version": "3.6.1",
      "os_name": "posix",
      "platform_machine": "x86_64",
      "platform_python_implementation": "CPython",
      "platform_release": "16.7.0",
      "platform_system": "Darwin",
      "platform_version": "Darwin Kernel Version 16.7.0: Thu Jun 15 17:36:27 PDT 2017; root:xnu-3789.70.16~2/RELEASE_X86_64",
      "python_full_version": "3.6.1",
      "python_version": "3.6",
      "sys_platform": "darwin"
    },
    "pipfile-spec": 5,
    "requires": {},
    "sources": [
      {
        "name": "pypi",
        "url": "https://pypi.python.org/simple",
        "verify_ssl": true
      }
    ]
  },
  "default": {
    "certifi": {
      "hashes": [
        "sha256:54a07c09c586b0e4c619f02a5e94e36619da8e2b053e20f594348c0611803704",
        "sha256:40523d2efb60523e113b44602298f0960e900388cf3bb6043f645cf57ea9e3f5"
      ],
      "version": "==2017.7.27.1"
    },
    "chardet": {
      "hashes": [
         "sha256:fc323ffcaeaed0e0a02bf4d117757b98aed530d9ed4531e3e15460124c106691",
         "sha256:84ab92ed1c4d4f16916e05906b6b75a6c0fb5db821cc65e70cbd64a3e2a5eaae"
      ],
      "version": "==3.0.4"
    },
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