list_meets_tuple.py

>>> x = [1]
>>> y = (2, 3)
>>> x + y
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can only concatenate list (not "tuple") to list
>>> x += y
>>> x
[1, 2, 3]

This is defensible in the sense that += is asymmetric (left side is special and gets to determine type)

whereas + is meant to be symmetric -- A + B vs B + A should almost always evaluate to the same value