I completed one of my “school’s-out” tasks today: I built a venting system for my coffee roaster. Now I can roast inside without filling my condo with acrid smoke!
(Well, too much acrid smoke. The seal between the exhaust attachment on top of the roaster and the vent tube isn’t perfect; I need to get some kind of female-to-female adapter for that connection.)
It turned out to be pretty easy. I cut a hole in a piece of plywood that I stuck a dryer vent draft blocker into. That’s attached to one end of the dryer vent tube with a worm drive clamp. The other end goes into an adjustable elbow, attached with another worm drive clamp. The Hearthware I-Roast 2 has a connector for hooking up to the female end of a 4″ dryer vent tube, so that just goes into the elbow, and that’s that.
After reading the Wikipedia article on derangements and seeing how one goes about finding the number of derangements of a given size, I figured out how to generate a random size-n derangement without generating all size-n derangements and picking one. This made my Secret Santa program rather more efficient (O(n) is just a little better than exponential time!)
Also, in writing this program, I found a point in Python where two of its paradigms don’t mix well. Like most languages with first-order functions, python has map() and reduce() functions. However, method calls are handled more like C++ or Java: you call them as object.methodname(). If you want to get a list of results of a method applied to each element of a list, there doesn’t appear to be a straightforward way to do it. In this case, I wanted to strip whitespace from a list of strings. I ended up using a lambda that takes a string s and returns s.strip(), which isn’t too clumsy.
Edit: One of my friends noted that this could be handled nicely with a list comprehension. D’oh! Fixed, though the original line has been left in, commented.
For those who are interested:
# Takes a list of strings on standard input (one per line)
# and prints it out alongside a random derangement of the list.
# Can be used for secret-Santa-type gift-giving arrangements.
# Copyright (C) 2007 Neal Groothuis
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http ://www.gnu.org/licenses/>.
def swapElements(i, j, l):
l[i], l[j] = l[j], l[i]
return [1, 0]
return swapElements(k, n-1, randomDerangement(n-1)+[n-1])
#names=map(lambda(s): s.strip(), sys.stdin.readlines())
names=[s.strip() for s in sys.stdin.readlines()]
for i in range(n):