• User's name is A. Eggenberger, so his username is a.eggenberger
• Default temporary folder is C:\Users\A9447~1.EGG
• pkg_resources considers a folder to be an "egg" if its name ends in .egg

>>> def f():
...     if 0:
...         break  # This is a syntax error!
...     print("Hello")
... 
>>> f()
Hello

>>> from datetime import datetime, timedelta, timezone
>>> class DatetimeSubclass(datetime): pass
...

>>> DatetimeSubclass.fromtimestamp(1607167800.0)
DatetimeSubclass(2020, 12, 5, 6, 30)

>>> DatetimeSubclass.fromtimestamp(1607167800.0, timezone.utc)
datetime.datetime(2020, 12, 5, 11, 30, tzinfo=datetime.timezone.utc)

No battle plan survives contact with the enemy. [N]o plan of operations extends with any certainty beyond the first contact with the main hostile force.

Desire paths

Unfamiliar environments

From @_saljam's April 2020 Twitter Thread on RTL bugs.

The real-word implications from my world are this: if your code has "if 0:" clauses in it, and you measure its coverage, then because the lines have not been optimized away, coverage.py will think the lines are a possible execution path, and will be considered a miss because they are not executed. This will reduce your coverage percentage.

def f() -> int:
    if 0:
        print("This code is unreachable!")

    if not __debug__:
        print("Running in optimized mode!")

    return 3

Packaging in Python: A Tale of Woe

In Python 2.0, distutils was added to the standard library. This allowed distro maintainers:

1. A standard way of converting Python projects into Linux distro packages
2. System administrators a standard way of installing them directly onto target systems

Package authors would write a setup.py that runs distutils.core.setup(), and end users would execute any number of commands via setup.py <command> (e.g. setup.py install and setup.py test).

The sheer amount of features that Setuptools brings to the table must be stressed: namespace packages, optional dependencies, automatic manifest building by inspecting version control systems, web scraping to find packages in unusual places, recognition of complex version numbering schemes, and so on, and so on. Some of these features perhaps seem esoteric to many, but complex projects use many of them.

$ pip install attrs
Collecting attrs
  Downloading attrs-20.3.0.tar.gz (164 kB)
     |████████████████████████████████| 164 kB 6.1 MB/s
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... done
Building wheels for collected packages: attrs
  Building wheel for attrs (PEP 517) ... done
  Created wheel for attrs: filename=attrs-20.3.0-py2.py3-none-any.whl size=49337
                           sha256=a6b44de70bcc7834e967dbea0b96c5f1ad03d438227c1e78f5dcbfbeb338607c
  Stored in directory: ~/.cache/pip/wheels/a4/3a/c7/ae1b7ae92f377604b64cab81594eb43ea843376139f34cc8a5
Successfully built attrs
Installing collected packages: attrs
Successfully installed attrs-20.3.0

Packaging Problems: The Tangled Web

• distribute: Imported as import setuptools
• setuptools: Monkey-patches distutils
• pip: Always injected import setuptools into setup.py commands

Packaging Problems: Churn

• distutils: ✘Frozen, deprecated
• distribute: ○Merged into setuptools
• distutils2: ✘Abandoned
• setuptools: ✔ Maintained
  • Most setup.py commands: ✘Deprecated or Removed
  • easy_install: ✘Deprecated
  • pkg_resources: ✘Semi-deprecated
• pip: ✔ Maintained

• PEP 440 - Version Identification and Dependency Specification
• PEP 453 - Explicit bootstrapping of pip in Python installations
• PEP 503 - Simple Repository API
• PEP 508 - Dependency Specification for Python Software Packages
• PEP 513 - A Platform Tag for Portable Linux Built Distributions

Churn budget

• How important is the change?
• How many people will it affect?
• How painful will it be for affected users?
• How much goodwill have you spent recently?

The Stable Interface Paradox