wai-lazypip

Allows installation of additional packages at runtime (from within virtual environments). Uses pip underneath the hood for installing the packages.

Installation

You can install the library with pip as follows:

pip install wai.lazypip

Functionality

The following methods are available from module wai.lazypip:

• check_module - checks whether the module is present and, if a list of packages has been provided, installs these and performs check again.
• require_module - like check_module, but instead of returning a boolean, will raise an Exception in case the module is not present.
• check_fun and require_fun work in a similar fashion, but checking for a function within the module.
• check_attr and require_attr check for an attribute within the module.
• check_class and require_class check for a class to be present within the module.

The list of packages to install is in the same format as you would normally pass on to the pip command-line too, e.g.:

["matplotlib"]
["matploblib<3.3.0"]

It is also possible to provide additional arguments to pip (which get inserted after the install argument).

Examples

• checking whether we are in a virtual environment

  from wai.lazypip import is_venv
  if is_venv():
      print("yep, in a virtual environment")
  else:
      print("sorry, not a virtual environment")

• checking for the matplotlib module and installing matplotlib older than 3.3.0 if not yet present in the virtual environment

  from wai.lazypip import check_module
  m = "matplotlib"
  p = [m + "<3.3.0"]
  print(m, check_module(m, p))

• checking whether the matplotlib module has method validate_backend and installing matplotlib older than 3.3.0 if not yet present in the virtual environment

  from wai.lazypip import check_fun
  m = "matplotlib"
  f = "validate_backend"
  p = [m + "<3.3.0"]
  print(m, f, check_fun(m, f, p))

• checking whether the matplotlib module has attribute URL_REGEX and installing matplotlib older than 3.3.0 if not yet present in the virtual environment

  from wai.lazypip import check_attr
  m = "matplotlib"
  a = "URL_REGEX"
  p = [m + "<3.3.0"]
  print(m, a, check_attr(m, a, p))

• checking whether the matplotlib module has method validate_backend and installing matplotlib older than 3.3.0 if not yet present in the virtual environment

  from wai.lazypip import check_class
  m = "matplotlib"
  c = "MutableMapping"
  p = [m + "<3.3.0"]
  print(m, c, check_class(m, c, p))