LSSTApplications  18.1.0
LSSTDataManagementBasePackage
doImport.py
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1 # This file is part of utils.
2 #
3 # Developed for the LSST Data Management System.
4 # This product includes software developed by the LSST Project
5 # (http://www.lsst.org).
6 # See the COPYRIGHT file at the top-level directory of this distribution
7 # for details of code ownership.
8 #
9 # This program is free software: you can redistribute it and/or modify
10 # it under the terms of the GNU General Public License as published by
11 # the Free Software Foundation, either version 3 of the License, or
12 # (at your option) any later version.
13 #
14 # This program is distributed in the hope that it will be useful,
15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 # GNU General Public License for more details.
18 #
19 # You should have received a copy of the GNU General Public License
20 # along with this program. If not, see <http://www.gnu.org/licenses/>.
21 
22 
23 import importlib
24 
25 __all__ = ("doImport",)
26 
27 
28 def doImport(importable):
29  """Import a python object given an importable string and return it.
30 
31  Parameters
32  ----------
33  importable : `str`
34  String containing dot-separated path of a Python class, module,
35  or member function.
36 
37  Returns
38  -------
39  type : `type`
40  Type object. Either a module or class or a function.
41 
42  Raises
43  ------
44  TypeError
45  ``importable`` is not a `str`.
46  ModuleNotFoundError
47  No module in the supplied import string could be found.
48  ImportError
49  ``importable`` is found but can not be imported or the requested
50  item could not be retrieved from the imported module.
51  """
52  if not isinstance(importable, str):
53  raise TypeError(f"Unhandled type of importable, val: {importable}")
54 
55  def tryImport(module, fromlist):
56  pytype = importlib.import_module(module)
57  # Can have functions inside classes inside modules
58  for f in fromlist:
59  try:
60  pytype = getattr(pytype, f)
61  except AttributeError:
62  raise ImportError(f"Could not get attribute '{f}' from '{module}'")
63  return pytype
64 
65  # Go through the import path attempting to load the module
66  # and retrieve the class or function as an attribute. Shift components
67  # from the module list to the attribute list until something works.
68  moduleComponents = importable.split(".")
69  infileComponents = []
70 
71  while moduleComponents:
72  try:
73  pytype = tryImport(".".join(moduleComponents), infileComponents)
74  if not infileComponents and hasattr(pytype, moduleComponents[-1]):
75  # This module has an attribute with the same name as the
76  # module itself (like doImport.doImport, actually!).
77  # If that attribute was lifted to the package, we should
78  # return the attribute, not the module.
79  try:
80  return tryImport(".".join(moduleComponents[:-1]), moduleComponents[-1:])
81  except ModuleNotFoundError:
82  pass
83  return pytype
84  except ModuleNotFoundError:
85  # Move element from module to file and try again
86  infileComponents.insert(0, moduleComponents.pop())
87 
88  raise ModuleNotFoundError(f"Unable to import {importable}")
def doImport(importable)
Definition: doImport.py:28