🕵️ Stack Trace Lineup

from contextvars import ContextVar
v = ContextVar("v")
v.get()

Traceback (most recent call last):
  File "lineup.py", line 3, in <module>
    v.get()
    ~~~~~^^
LookupError: <ContextVar name='v' at 0x104517d80>

from fractions import Fraction
Fraction("1/0")

Traceback (most recent call last):
  File "lineup.py", line 2, in <module>
    Fraction("1/0")
    ~~~~~~~~^^^^^^^
ZeroDivisionError: Fraction(1, 0)

class Base:
    def __init_subclass__(cls, req, **kw):
        super().__init_subclass__(**kw)

class C(Base): pass

Traceback (most recent call last):
  File "lineup.py", line 5, in <module>
    class C(Base): pass
TypeError: Base.__init_subclass__() missing 1 required positional argument: 'req'

class D(dict):
    def __missing__(self, k):
        return "default"

d = D()
print(d["x"])
print(d)

Traceback (most recent call last):
  File "lineup.py", line 6, in <module>
    print(d["x"])
          ~^^^^^
RuntimeError: __missing__ returned but key not stored in dict

import warnings
warnings.simplefilter("bogus")

Traceback (most recent call last):
  File "lineup.py", line 2, in <module>
    warnings.simplefilter("bogus")
    ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/usr/lib/python3.13/_py_warnings.py", line 305, in simplefilter
    raise ValueError(f"invalid action: {action!r}")
ValueError: invalid action: 'bogus'