[Tutor] Obfuscated Python [was Long Lines techniques]

[Avi Gross]

Steven,

There are dunderheads who will maliciously misuse things. Yes, we know what
__add__ is supposed to do. But if someone codes a class with one that
ignores addition to a collection if it has reached a maximum size, or does
addition modulo 16 or makes it play a happy birthday tune, while
subtracting, it may not be trivial for the innocent user of your code to
make much sense of it. 

There are documented IDEAS about what many of those dunder methods might
mean but no enforcement. 

I remember an Abstract Algebra course I took where we often talked about
operations like + and * in very abstract ways and came up with some
fascinating meanings to the operations. An example might be the various
definitions of multiplication for vectors or matrices. When you multiply,
are you multiplying corresponding parts or are you multiplying a row times a
column and summing the multiplications for each slot in the matrix? Or could
multiplication be a tad more complex and require also taking a transpose
first? Or perhaps getting a determinant or eigenvalues or eigenvectors? What
does it mean to add "1" to a complex number or quaternion or octonion? 

The reality is that two people can often try to make a similar class and
come up with different ideas and implementations. If I have a class
representing people who RSVP for a party, might a PLUS of a person result in
upping the party count by 2 since we assume they are bringing a date and if
their presence requires another table, upping that count and so on? A simple
__add__ can result in many things such as checking the added person for
dietary needs and adjusting more stuff just because adding a person can be
complex.

You re not going to sucker me into discussing obfuscation today. Some people
here got touchy last time.

I am not defending PERL nor slamming Python. I am saying people who behave
well will try to avoid writing code that is hard to read and may be
understood in multiple ways. There are cute ways to do things in many
languages.

Last comment, in what some might call stream of consciousness. Python allows
a function to return without an explicit return. Usually it returns None but
I not in some generators it may throw an exception instead. The problem is
that if you are not looking carefully at indentation, you might thing the
statements that follow may be part of the same function. So my personal
preference is to have an explicit return instead of letting it drop out of
the function or at least a comment saying this is the end of the function.
Similarly, many people won't close a file (I am not talking about in a with
statement) or delete variables no longer in use, and depend on these things
happening automatically eventually. There may be nothing wrong with that,
especially for smaller programs. But a part of me appreciates when the
scales are visibly balanced. But when overdone, as in a function where every
statement is in its own try/catch even for problems very unlikely to happen,
there is too muc detail to follow. Something in between seems more
comfortable. So interrupting an algorithm to del no longer needed variables
may not be best either. To each their own.

-----Original Message-----
From: Tutor <tutor-bounces+avigross=verizon.net at python.org> On Behalf Of
Steven D'Aprano
Sent: Friday, December 14, 2018 12:36 AM
To: tutor at python.org
Subject: [Tutor] Obfuscated Python [was Long Lines techniques]

On Thu, Dec 13, 2018 at 11:07:59PM -0500, Avi Gross wrote:

> Python may claim to be straightforward but I can easily see ways to 
> fool people in python too with dunder methods or function closures or 
> decorators or ...

Dunder methods shouldn't fool anyone. Each dunder method has a
straightforward use, and most of the time you can guess that they do. 
__add__ implements the + operator, etc.

Closures and decorators can be abused, as can anything. One can write
obfuscated code in any language. Here's some amusing obfuscated Python:

https://www.reddit.com/r/Python/comments/i1qgp/reduce_and_lambda_two_great_t
astes_that_taste/

https://mail.python.org/pipermail/python-list/2013-October/658470.html

Anyone else want to share some obfuscated Python code?



--
Steve
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