On Sunday, January 11, 2015 at 8:02:50 AM UTC+5:30, Steven D'Aprano wrote: > Rick Johnson wrote: > > > > ============================================================ > > EXAMPLE 1: "Reducing Comprehension" > > https://docs.python.org/2/howto/doanddont.html#using-the-batteries > > ============================================================ > > > > > > ############################################################ > > # QUOTE: Python Docs # > > ############################################################ > > # Another highly useful function is reduce() which can be # > > # used to repeatly apply a binary operation to a sequence, # > > # reducing it to a single value. For example, compute a # > > # factorial with a series of multiply operations: # > > # # > > # py> n = 4 # > > # py> import operator # > > # py> reduce(operator.mul, range(1, n+1)) # > > # 24 # > > ############################################################ > > > How exactly does: assigning variables(n = 4), > > arithmetic(n+1), and the "range" function going to help me > > understand the usefulness of the reduce function? > > Obviously they don't, duh. They're mere incidentals. > > > > A much better example would be: > > > > py> import operator > > py> reduce(operator.mul, [1,2,3,4]) > > 24 > > "But Rick, my o-so-wise teacher, what's this stuff with the square brackets > and commas? And the round brackets (or parentheses as the Americans call > them)?" > > At the point you are demonstrating reduce(), if the reader doesn't > understand or can't guess the meaning of "n = 4", "n+1" or range(), they > won't understand anything you say. > > Teachers need to understand that education is a process of building upon > that which has come before. If the teacher talks down to the student by > assuming that the student knows nothing, and tries to go back to first > principles for every little thing, they will never get anywhere. > > In this case, it is perfectly acceptable to assume that by the time the > beginner gets to a document about "Dos and Don'ts" they are comfortable > with such basic concepts as assigning values to variables "n=4", > addition "n+1", importing, and can interpret from the context that > operator.mul multiplies without needing to be explicitly told. > > If you treat your readers as idiots, only idiots will read your writing. > > > > At *LEAST* with that example the only potential unknown > > might be "operator.mul". However, a wise teacher would > > recognize that this is a fine "teaching example" of how > > using the operator module can prevent duplicating code -- > > And the version on the docs demonstrates this by example, instead of > patronising the reader and treating them as an eight year old who needs to > have the most trivial things explained to them. > > > > which would lead to a better example like: > > > > py> def mul(x, y): > > ... return x*y > > py> reduce(mul, [1,2,3,4]) > > 24 > > "But Rick, my o-so-wise teacher! What is the meaning of 'def', 'return' and > the asterisk between the x and y? What's with the three dots and the > spaces?" > > > > > FINALLY! An example that showcases a proper usage of the > > the reduce function *WITHOUT* any superfluous distractions. > > Apart from having to define your own function. Given that this is a document > intended to show-case best practice (as in Do this, Don't do that) it is > completely inappropriate to encourage the reader to re-invent the wheel by > creating their own (slow) mul function instead of importing the (fast) > pre-built one in the operator module. > > > > However, > > remembering that code re-use is a good thing, and that re- > > inventing the wheel is a lot of work, we should mention that > > the "mul" function should be replaced with "operator.mul" > > No, we should not "mention" it as an aside. We should demonstrate best > practice from the start. Unless you are writing for beginners who haven't > been introduced to importing yet (in which case, why are you teaching them > reduce() so early?) there is no benefit at all in showing people how *not* > to do it, then jokingly give them a little nudge-nudge-wink-wink "by the > way, this is better" aside. > > > > Note: Be sure to check out the "operator" module for > > pre-defined arithmetic functions like "operator.mul", > > which would "reduce" (*wink*) the above code to this: > > > > py> reduce(operator.mul, [1,2,3,4]) > > 24 > > > > > > ============================================================ > > EXAMPLE 2: "The Fibonacci Phallus Extender". > > > And that's where I stopped reading. I'm sure it will be overflowing with > insights of your usual quality, but I hurt myself laughing so hard at your > wit ("ha ha, phallus, that means the D") that I simply couldn't continue. > > > > -- > Steven
Rick: Your style beyond irritating to just plain ridiculous. As it happens I find your reduce example better than the given one. Unfortunately dunno how to agree the one and not the other :-) -- https://mail.python.org/mailman/listinfo/python-list
