Hard Python Dictionary Exercise (lemmy.nz)

submitted 2 weeks ago by bterwijn@programming.dev to c/python@programming.dev

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A hard exercise to help build the right mental model for Python data.

The “Solution” link visualizes execution and reveals what’s actually happening using 𝗺𝗲𝗺𝗼𝗿𝘆_𝗴𝗿𝗮𝗽𝗵: https://github.com/bterwijn/memory_graph

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[-] syklemil@discuss.tchncs.de 5 points 2 weeks ago

I didn't have previous exposure to that exact syntax either, but:

Python and plenty other languages have assignment variations with an operator like +
| in plenty of languages means logical OR
- possibly bitwise, but that seems unlikely in Python
Dicts are sorta complex siblings of sets
In terms of sets, OR is equivalent to a union

Hence, a |=b should have the same meaning as a = a | b or a = a.union(b)

and then the quiz is about basically implementation details and what the actual semantics winds up being in a language like python, where stuff is mutable by default and references are implicit (even though the zen of python states a preference for being explicit)

[-] bterwijn@programming.dev 3 points 2 weeks ago* (last edited 2 weeks ago)

There is one important difference between a |= b and a = a | b, that is one part that makes this exercise difficult. See the dictionary docs (https://docs.python.org/3/builtins/stdtypes.html#dict):

d |= other Update the dictionary d with keys and values from other, which may be either a mapping or an iterable of key/value pairs. The values of other take priority when d and other share keys. Added in version 3.9.

Pick your answer and check the Solution link.

The zen of Python lies unless you're Dutch. I'm Dutch and when I look out of my office I see the CWI where Guido wrote the original Python versions back in the day, see "Python the documentory" on YouTube.