Python packaging series:

Welcome to the third installment of what now I call the “Python packaging series”.

Last time I wrote about my progress and lessons learned while creating the ignition-api Python package, and a lot has happened in the last eight months, so let me fill you in.

  • In March 2022, the ignition-api GitHub organization was born
    • With that, each branch of the thecesrom/Ignition repo was moved into its own repo; jython, 7.9, 8.0, and 8.1
  • In June 29 2022, ignition-api-stubs got its Alpha release, and a month later it got its Beta release
    • Some valuable knowledge in typing was gained (more on stubgen and TypedDict in another post)
  • git-cliff was replaced by commitizen on actively developed repos

That pretty much sums up the last couple of months.

And now, onto our main topic.

As I continued working on improving and adding type hints (or comments) in baby steps to the ignition-api package, and then decided to accept Unicode literals and not just str, I added the following import to all modules:

from __future__ import unicode_literals

The reason why I decided to create an alias called String instead of using AnyStr from typing escapes me at this moment, but a quick test shows that mypy throws an error in a function where I specifically return unicode; so maybe that was the “why”.

String = Union[str, unicode]

After some debate, I decided to refactor my code and move the String alias to java.lang, where it belonged all along. Enter commit ea530ac.

ignition-api 8.1.13 was released in December 2021, and I did not realize my mistake until January 2022 when I upgraded my virtual environment for my incendium project and tried to run pip list, only then it dawned upon me I had pushed a bad release.

Once anyone updated to ignition-api 8.1.13, pip under their Python environment (or installation) ceased to work, and it threw the following error:

Traceback (most recent call last):
  File "/Users/thecesrom/.pyenv/versions/2.7.18/lib/python2.7/", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/Users/thecesrom/.pyenv/versions/2.7.18/lib/python2.7/", line 72, in _run_code
    exec code in run_globals
  File "/Users/thecesrom/.pyenv/versions/2.7.18/envs/incendium/lib/python2.7/site-packages/pip/", line 23, in <module>
    from pip._internal.cli.main import main as _main  # isort:skip # noqa
  File "/Users/thecesrom/.pyenv/versions/incendium/lib/python2.7/site-packages/pip/_internal/cli/", line 10, in <module>
    from pip._internal.cli.autocompletion import autocomplete
  File "/Users/thecesrom/.pyenv/versions/incendium/lib/python2.7/site-packages/pip/_internal/cli/", line 4, in <module>
    import optparse
  File "/Users/thecesrom/.pyenv/versions/2.7.18/lib/python2.7/", line 90, in <module>
    from gettext import gettext
  File "/Users/thecesrom/.pyenv/versions/2.7.18/lib/python2.7/", line 49, in <module>
    import locale, copy, os, re, struct, sys
  File "/Users/thecesrom/.pyenv/versions/2.7.18/lib/python2.7/", line 60, in <module>
    from org.python.core import PyStringMap
  File "/Users/thecesrom/.pyenv/versions/incendium/lib/python2.7/site-packages/org/python/core/", line 5, in <module>
    from java.lang import Object
  File "/Users/thecesrom/.pyenv/versions/incendium/lib/python2.7/site-packages/java/lang/", line 22, in <module>
    from typing import Union
  File "/Users/thecesrom/.pyenv/versions/incendium/lib/python2.7/site-packages/", line 1440, in <module>
    copy._copy_dispatch[GenericMeta] = _copy_generic
AttributeError: 'module' object has no attribute '_copy_dispatch'

I immediately panicked, and reverted the java.lang.String change, and released ignition-api 8.1.13.post1.

Searching the Internet gave me no answers. Apparently no one had seen or experienced something like this.

Admitting defeat, I left things as they were for a while, but after a while I went back and followed the breadcrumbs - or should I say traceback?

copy._copy_dispatch[GenericMeta] = _copy_generic

That was not it.


String = Union[str, unicode]

That was not meaningful.


from java.lang import Object

What??? Onto the next one.

    from org.python.core import PyStringMap  # this is line 60
except ImportError:
    PyStringMap = None

But why?

If my mocking of org.python.core within ignition-api was to blame, wasn’t this supposed to be caught as the ImportError?

The answer is: No.

So I tried adding the following line, and same thing.

PyStringMap = None

The solution came to me by accident, because while I was editing on Visual Studio Code it automatically added the import statement which solved my issue.

from copy import PyStringMap

Something I would have never thought of doing, but it fixed my issue. Issue ignition-api/8.1#28 was created and immediately fixed by PR ignition-api/8.1#29.

$ git diff e4d494e 3beb4d5 src/org/python/core/
diff --git a/src/org/python/core/ b/src/org/python/core/
index 0f4e826..4f36856 100644
--- a/src/org/python/core/
+++ b/src/org/python/core/
@@ -1,8 +1,15 @@
 from __future__ import print_function

-__all__ = ["PyObject", "PyType"]
+from copy import PyStringMap

-from java.lang import Object
+__all__ = ["PyObject", "PyStringMap", "PyType"]

And with that, my friends, the AttributeError: 'module' object has no attribute '_copy_dispatch' bug was squashed.

Thanks for reading!

P.S. lines 59-63 were committed by no other than @gvanrossum back in November 27, 2000 in f8baad0 which took 21 years to come bite me (or save me?)