Project P019
Poll
Set up a poll with two to six options, enter ranked ballots (one at a time or many identical ones at once), and count them four ways side by side - plurality, instant runoff round by round, Borda, and head to head - to see when the methods disagree, from a text menu.
3 modules · 3 recorded sessionstext-menu UI in the terminalupdated 2026-10-03
Every screen below was recorded under CPython. When this page was built, the EML interpreter replayed each session from the same input and printed the same bytes.
About
Set up a poll - a question and two to six options, lettered A to F - enter ranked ballots, and count them four ways side by side: plurality, instant runoff (round by round), Borda, and head to head. The four methods often agree; the program is built to show it plainly when they do not. A text menu; the poll lives while the program runs.
main.eml- the menu, setting up a poll, reading ballots, and the results and ballot screenscount.eml- the four counts, the instant-runoff rounds, and the head-to-head winnertext.eml- trimming, capitals, whole numbers, words and percentages
A ballot ranks options by letter, most preferred first ("B A C", "bac" or "c,b"), and need not rank them all. A count in front ("40 A B C") enters that many identical ballots - the way paper ballots are tallied.
The four counts:
- Plurality: only first choices count; the most wins.
- Instant runoff: count first choices among the options still in; an option with more than half of the ballots still counting wins; otherwise the option with the fewest goes out and its ballots move to their next choice. A ballot with no choice left is exhausted and counts for no one. A tie for fewest is broken by the fewest first choices in the first round, then by the option listed later.
- Borda: with k options, first place earns k - 1 points, second k - 2, and so on; an option a ballot leaves unranked earns nothing.
- Head to head: every pair of options, counting the ballots that put one above the other (an unranked option is below every ranked one). The winner is the option that beats every other; there may be none.
What is checked: a question has at most 60 characters and an option at most 20, options are not repeated in any case, and a poll needs at least two (a failed setup leaves the old poll as it was); a ballot uses only the poll's letters, each once, with a count from 1 to 1000 if any.
Sessions: sessions/basic.in has 100 voters choose a library site 40/35/25, where plurality and instant runoff pick Riverside while Borda and head to head pick Hilltop, the option nobody puts last; sessions/strategic.in counts a club vote twice - sincere, Borda elects the second choice of the 55-voter majority, and when those voters rank it last instead, Borda elects their own first choice; sessions/bad-input.in types questions, options and ballots that are empty, too long, repeated, outside the letters or with a count out of range, then counts a poll whose instant runoff needs both tie-breaks and exhausts ballots, and where no option beats every other.
Built on the verified corpus cases the-runoff-eliminated-the-one-everyone-could-accept (instant runoff eliminating the option that would beat each other one head to head) and the-sincere-ballot-lost-to-the-strategic-one (a Borda count won by burying a real second choice).
Recorded sessions
What the screen shows while someone uses the program. Each typed line appears after its prompt, the way a terminal shows it.
bad-input
interpreter: byte-equal
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 7
Pick a number from 1 to 5.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 2
Set up a poll first.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 3
No ballots yet.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 4
No ballots yet.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 1
question>
Cancelled.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 1
question> A question that is far too long to fit in the sixty characters allowed
At most 60 characters.
question> Is it fine?
Options, one per line - 2 to 6; an empty line ends the list.
option A> Yes
option B> yes
That option is already there.
option B>
A poll needs at least two options; nothing changed.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 1
question> Tea or coffee?
Options, one per line - 2 to 6; an empty line ends the list.
option A> Tea
option B> Coffee
option C> A name that is far too long
At most 20 characters.
option C> Water
option D>
Poll ready: Tea or coffee?
A) Tea B) Coffee C) Water
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 3
No ballots yet.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 2
Rank by letter, most preferred first (like B A), or put a count first for that many identical ballots (like 40 A B). An empty line ends voting.
ballot> D
Type letters from A to C, each once, with a count from 1 to 1000 in front if you like.
ballot> A A
Type letters from A to C, each once, with a count from 1 to 1000 in front if you like.
ballot> 0 A
Type letters from A to C, each once, with a count from 1 to 1000 in front if you like.
ballot> 1001 B
Type letters from A to C, each once, with a count from 1 to 1000 in front if you like.
ballot> x
Type letters from A to C, each once, with a count from 1 to 1000 in front if you like.
ballot> 3 a
Counted 3 ballots: A.
ballot> c,b
Counted 1 ballot: C > B.
ballot> c
Counted 1 ballot: C.
ballot> 2 b
Counted 2 ballots: B.
ballot>
7 ballots so far.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 4
-- ballots: 7 ballots, 4 different rankings --
3 A
1 C > B
1 C
2 B
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 3
Question: Tea or coffee?
-- results: 7 ballots --
Plurality - first choices only:
A) Tea 3 42.9%
B) Coffee 2 28.6%
C) Water 2 28.6%
winner: Tea
Instant runoff - the last goes out and its ballots move to their next choice:
round 1: Tea 3, Coffee 2, Water 2 - Water goes out
round 2: Tea 3, Coffee 3 - Coffee goes out (1 ballot with no choice left)
round 3: Tea 3 - Tea has more than half of 3 (4 ballots with no choice left)
winner: Tea
Borda - 2 points for first place, one less for each place below:
Tea 6, Coffee 5, Water 4
winner: Tea
Head to head - every pair of options, one against the other:
Tea and Coffee tie 3 to 3
Tea beats Water 3 to 2
Coffee and Water tie 2 to 2
no option beats every other one
Winners: plurality Tea; instant runoff Tea; Borda Tea; head to head none.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 5
Bye.
What was typed (34 lines)
7
2
3
4
1
1
A question that is far too long to fit in the sixty characters allowed
Is it fine?
Yes
yes
1
Tea or coffee?
Tea
Coffee
A name that is far too long
Water
3
2
D
A A
0 A
1001 B
x
3 a
c,b
c
2 b
4
3
5
basic
interpreter: byte-equal
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 1
question> Where should the new library go?
Options, one per line - 2 to 6; an empty line ends the list.
option A> Riverside
option B> Hilltop
option C> Downtown
option D>
Poll ready: Where should the new library go?
A) Riverside B) Hilltop C) Downtown
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 2
Rank by letter, most preferred first (like B A), or put a count first for that many identical ballots (like 40 A B). An empty line ends voting.
ballot> 40 A B C
Counted 40 ballots: A > B > C.
ballot> 35 C B A
Counted 35 ballots: C > B > A.
ballot> 25 B A C
Counted 25 ballots: B > A > C.
ballot>
100 ballots so far.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 3
Question: Where should the new library go?
-- results: 100 ballots --
Plurality - first choices only:
A) Riverside 40 40.0%
C) Downtown 35 35.0%
B) Hilltop 25 25.0%
winner: Riverside
Instant runoff - the last goes out and its ballots move to their next choice:
round 1: Riverside 40, Downtown 35, Hilltop 25 - Hilltop goes out
round 2: Riverside 65, Downtown 35 - Riverside has more than half of 100
winner: Riverside
Borda - 2 points for first place, one less for each place below:
Hilltop 125, Riverside 105, Downtown 70
winner: Hilltop
Head to head - every pair of options, one against the other:
Hilltop beats Riverside 60 to 40
Riverside beats Downtown 65 to 35
Hilltop beats Downtown 65 to 35
winner: Hilltop, who beats every other option
Winners: plurality Riverside; instant runoff Riverside; Borda Hilltop; head to head Hilltop.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 4
-- ballots: 100 ballots, 3 different rankings --
40 A > B > C
35 C > B > A
25 B > A > C
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 5
Bye.
What was typed (14 lines)
1
Where should the new library go?
Riverside
Hilltop
Downtown
2
40 A B C
35 C B A
25 B A C
3
4
5
strategic
interpreter: byte-equal
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 1
question> Which design should the club pick?
Options, one per line - 2 to 6; an empty line ends the list.
option A> Alder
option B> Birch
option C> Cedar
option D>
Poll ready: Which design should the club pick?
A) Alder B) Birch C) Cedar
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 2
Rank by letter, most preferred first (like B A), or put a count first for that many identical ballots (like 40 A B). An empty line ends voting.
ballot> 55 A B C
Counted 55 ballots: A > B > C.
ballot> 45 B C A
Counted 45 ballots: B > C > A.
ballot>
100 ballots so far.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 3
Question: Which design should the club pick?
-- results: 100 ballots --
Plurality - first choices only:
A) Alder 55 55.0%
B) Birch 45 45.0%
C) Cedar 0 0.0%
winner: Alder
Instant runoff - the last goes out and its ballots move to their next choice:
round 1: Alder 55, Birch 45, Cedar 0 - Alder has more than half of 100
winner: Alder
Borda - 2 points for first place, one less for each place below:
Birch 145, Alder 110, Cedar 45
winner: Birch
Head to head - every pair of options, one against the other:
Alder beats Birch 55 to 45
Alder beats Cedar 55 to 45
Birch beats Cedar 100 to 0
winner: Alder, who beats every other option
Winners: plurality Alder; instant runoff Alder; Borda Birch; head to head Alder.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 1
question> Which design should the club pick?
Options, one per line - 2 to 6; an empty line ends the list.
option A> Alder
option B> Birch
option C> Cedar
option D>
Poll ready: Which design should the club pick?
A) Alder B) Birch C) Cedar
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 2
Rank by letter, most preferred first (like B A), or put a count first for that many identical ballots (like 40 A B). An empty line ends voting.
ballot> 55 A C B
Counted 55 ballots: A > C > B.
ballot> 45 B C A
Counted 45 ballots: B > C > A.
ballot>
100 ballots so far.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 3
Question: Which design should the club pick?
-- results: 100 ballots --
Plurality - first choices only:
A) Alder 55 55.0%
B) Birch 45 45.0%
C) Cedar 0 0.0%
winner: Alder
Instant runoff - the last goes out and its ballots move to their next choice:
round 1: Alder 55, Birch 45, Cedar 0 - Alder has more than half of 100
winner: Alder
Borda - 2 points for first place, one less for each place below:
Alder 110, Cedar 100, Birch 90
winner: Alder
Head to head - every pair of options, one against the other:
Alder beats Birch 55 to 45
Alder beats Cedar 55 to 45
Cedar beats Birch 55 to 45
winner: Alder, who beats every other option
Winners: plurality Alder; instant runoff Alder; Borda Alder; head to head Alder.
== Poll ==
1) new poll 2) vote 3) results 4) ballots 5) quit
choice> 5
Bye.
What was typed (23 lines)
1
Which design should the club pick?
Alder
Birch
Cedar
2
55 A B C
45 B C A
3
1
Which design should the club pick?
Alder
Birch
Cedar
2
55 A C B
45 B C A
3
5
Modules
The program as written, entry module first. Each module transpiles to its own Python file, which is what eml project run executes.
main.eml(entry)
eml# P019 poll: set up a poll, enter ranked ballots, and count them four ways
# side by side - plurality, instant runoff, Borda and head to head - so that
# when the methods disagree, the disagreement is on the screen.
import count
import text
"ABCDEF" => letters
6 => most_options
1000 => most_at_once
def plural(n, word):
if n == 1:
return "1 " + word
return str(n) + " " + word + "s"
def names_text(options, items):
# "Riverside", "Riverside and Downtown", "A, B and C".
if len(items) == 1:
return options[items[0]]
"" => out
for i in [0:len(items) - 2]:
if i > 0:
out + ", " => out
out + options[items[i]] => out
return out + " and " + options[items[len(items) - 1]]
def ranked(scores, k):
# The options from highest score to lowest; equal scores in option order.
[] => out
for i in [0:k - 1]:
len(out) => p
out + [i] => out
while p > 0 and scores[out[p - 1]] < scores[i]:
out[p - 1] => out[p]
p - 1 => p
i => out[p]
return out
def ask_text(prompt, longest):
# Text of at most longest characters, asked again until it fits; "" ends.
while True:
text.trim(input(prompt)) => answer
if len(answer) <= longest:
return answer
("At most " + str(longest) + " characters.") ^0
def parse_ballot(answer, k):
# [ranking, count] for a ballot like "B A C", "bac" or "40 B A C", or
# None if it is not one.
text.words(answer) => ws
1 => n
if len(ws) > 1 and text.number(ws[0]) >= 0:
text.number(ws[0]) => n
ws[1:len(ws)] => ws
if n < 1 or n > most_at_once:
return None
"" => typed
for w in ws:
typed + text.upper(w) => typed
if typed == "":
return None
[] => ranking
for c in typed:
0 - 1 => found
for i in [0:k - 1]:
if letters[i] == c:
i => found
if found == 0 - 1:
return None
for o in ranking:
if o == found:
return None
ranking + [found] => ranking
return [ranking, n]
def ranking_text(ranking):
"" => out
for p in [0:len(ranking) - 1]:
if p > 0:
out + " > " => out
out + letters[ranking[p]] => out
return out
def show_results(options, ballots):
len(options) => k
count.total(ballots) => n
"" ^0
("-- results: " + plural(n, "ballot") + " --") ^0
"Plurality - first choices only:" ^0
count.plurality(ballots, k) => votes
for i in ranked(votes, k):
(" " + letters[i] + ") " + ("%-20s" % options[i]) + ("%6d" % votes[i]) + ("%8s" % (text.tenths(100 * votes[i], n) + "%"))) ^0
count.leaders(votes, k) => top
if len(top) == 1:
(" winner: " + options[top[0]]) ^0
else:
(" tie: " + names_text(options, top)) ^0
[names_text(options, top)] => winners
"Instant runoff - the last goes out and its ballots move to their next choice:" ^0
count.runoff(ballots, k) => r
for i in [0:len(r[0]) - 1]:
r[0][i] => rd
"" => line
[] => still_in
for o in ranked(rd[0], k):
if not rd[3][o]:
still_in + [o] => still_in
for o in still_in:
if line != "":
line + ", " => line
line + options[o] + " " + str(rd[0][o]) => line
if rd[2] == 0 - 1:
line + " - " + options[r[1]] + " has more than half of " + str(rd[1]) => line
else:
line + " - " + options[rd[2]] + " goes out" => line
if rd[1] < n:
line + " (" + plural(n - rd[1], "ballot") + " with no choice left)" => line
(" round " + str(i + 1) + ": " + line) ^0
(" winner: " + options[r[1]]) ^0
winners + [options[r[1]]] => winners
("Borda - " + plural(k - 1, "point") + " for first place, one less for each place below:") ^0
count.borda(ballots, k) => points
"" => line
for i in ranked(points, k):
if line != "":
line + ", " => line
line + options[i] + " " + str(points[i]) => line
(" " + line) ^0
count.leaders(points, k) => top
if len(top) == 1:
(" winner: " + options[top[0]]) ^0
else:
(" tie: " + names_text(options, top)) ^0
winners + [names_text(options, top)] => winners
"Head to head - every pair of options, one against the other:" ^0
count.head_to_head(ballots, k) => wins
for i in [0:k - 2]:
for j in [i + 1:k - 1]:
if wins[i][j] > wins[j][i]:
(" " + options[i] + " beats " + options[j] + " " + str(wins[i][j]) + " to " + str(wins[j][i])) ^0
elif wins[j][i] > wins[i][j]:
(" " + options[j] + " beats " + options[i] + " " + str(wins[j][i]) + " to " + str(wins[i][j])) ^0
else:
(" " + options[i] + " and " + options[j] + " tie " + str(wins[i][j]) + " to " + str(wins[j][i])) ^0
count.beats_all(wins, k) => w
if w == 0 - 1:
" no option beats every other one" ^0
winners + ["none"] => winners
else:
(" winner: " + options[w] + ", who beats every other option") ^0
winners + [options[w]] => winners
("Winners: plurality " + winners[0] + "; instant runoff " + winners[1] + "; Borda " + winners[2] + "; head to head " + winners[3] + ".") ^0
"" => question
[] => options
[] => ballots
True => running
while running:
"" ^0
"== Poll ==" ^0
"1) new poll 2) vote 3) results 4) ballots 5) quit" ^0
text.trim(input("choice> ")) => choice
if choice == "1":
ask_text("question> ", 60) => q
if q == "":
"Cancelled." ^0
else:
("Options, one per line - 2 to " + str(most_options) + "; an empty line ends the list.") ^0
[] => new_options
while len(new_options) < most_options:
ask_text("option " + letters[len(new_options)] + "> ", 20) => name
if name == "":
break
False => clash
for o in new_options:
if text.upper(o) == text.upper(name):
True => clash
if clash:
"That option is already there." ^0
else:
new_options + [name] => new_options
if len(new_options) < 2:
"A poll needs at least two options; nothing changed." ^0
else:
q => question
new_options => options
[] => ballots
"" => listing
for i in [0:len(options) - 1]:
listing + " " + letters[i] + ") " + options[i] => listing
("Poll ready: " + question) ^0
listing ^0
elif choice == "2":
if len(options) == 0:
"Set up a poll first." ^0
else:
("Rank by letter, most preferred first (like " + letters[1] + " " + letters[0] + "), or put a count first for that many identical ballots (like 40 " + letters[0] + " " + letters[1] + "). An empty line ends voting.") ^0
while True:
text.trim(input("ballot> ")) => answer
if answer == "":
break
parse_ballot(answer, len(options)) => b
if b == None:
("Type letters from A to " + letters[len(options) - 1] + ", each once, with a count from 1 to " + str(most_at_once) + " in front if you like.") ^0
else:
ballots + [b] => ballots
("Counted " + plural(b[1], "ballot") + ": " + ranking_text(b[0]) + ".") ^0
(plural(count.total(ballots), "ballot") + " so far.") ^0
elif choice == "3":
if count.total(ballots) == 0:
"No ballots yet." ^0
else:
("Question: " + question) ^0
show_results(options, ballots)
elif choice == "4":
if count.total(ballots) == 0:
"No ballots yet." ^0
else:
[] => groups
for b in ballots:
False => merged
for g in groups:
if not merged and ranking_text(g[0]) == ranking_text(b[0]):
g[1] + b[1] => g[1]
True => merged
if not merged:
groups + [[b[0], b[1]]] => groups
"" ^0
("-- ballots: " + plural(count.total(ballots), "ballot") + ", " + plural(len(groups), "different ranking") + " --") ^0
for g in groups:
(("%6d" % g[1]) + " " + ranking_text(g[0])) ^0
elif choice == "5":
False => running
else:
"Pick a number from 1 to 5." ^0
"Bye." ^0
Python projection (main.py)
import count
import text
letters = "ABCDEF"
most_options = 6
most_at_once = 1000
def plural(n, word):
if n == 1:
return "1 " + word
return str(n) + " " + word + "s"
def names_text(options, items):
if len(items) == 1:
return options[items[0]]
out = ""
for i in range(0, len(items) - 2+1):
if i > 0:
out = out + ", "
out = out + options[items[i]]
return out + " and " + options[items[len(items) - 1]]
def ranked(scores, k):
out = []
for i in range(0, k):
p = len(out)
out = out + [i]
while p > 0 and scores[out[p - 1]] < scores[i]:
out[p] = out[p - 1]
p = p - 1
out[p] = i
return out
def ask_text(prompt, longest):
while True:
answer = text.trim(input(prompt))
if len(answer) <= longest:
return answer
print("At most " + str(longest) + " characters.")
def parse_ballot(answer, k):
ws = text.words(answer)
n = 1
if len(ws) > 1 and text.number(ws[0]) >= 0:
n = text.number(ws[0])
ws = ws[1:len(ws)]
if n < 1 or n > most_at_once:
return None
typed = ""
for w in ws:
typed = typed + text.upper(w)
if typed == "":
return None
ranking = []
for c in typed:
found = 0 - 1
for i in range(0, k):
if letters[i] == c:
found = i
if found == 0 - 1:
return None
for o in ranking:
if o == found:
return None
ranking = ranking + [found]
return [ranking, n]
def ranking_text(ranking):
out = ""
for p in range(0, len(ranking)):
if p > 0:
out = out + " > "
out = out + letters[ranking[p]]
return out
def show_results(options, ballots):
k = len(options)
n = count.total(ballots)
print("")
print("-- results: " + plural(n, "ballot") + " --")
print("Plurality - first choices only:")
votes = count.plurality(ballots, k)
for i in ranked(votes, k):
print(" " + letters[i] + ") " + "%-20s" % options[i] + "%6d" % votes[i] + "%8s" % (text.tenths(100 * votes[i], n) + "%"))
top = count.leaders(votes, k)
if len(top) == 1:
print(" winner: " + options[top[0]])
else:
print(" tie: " + names_text(options, top))
winners = [names_text(options, top)]
print("Instant runoff - the last goes out and its ballots move to their next choice:")
r = count.runoff(ballots, k)
for i in range(0, len(r[0])):
rd = r[0][i]
line = ""
still_in = []
for o in ranked(rd[0], k):
if not rd[3][o]:
still_in = still_in + [o]
for o in still_in:
if line != "":
line = line + ", "
line = line + options[o] + " " + str(rd[0][o])
if rd[2] == 0 - 1:
line = line + " - " + options[r[1]] + " has more than half of " + str(rd[1])
else:
line = line + " - " + options[rd[2]] + " goes out"
if rd[1] < n:
line = line + " (" + plural(n - rd[1], "ballot") + " with no choice left)"
print(" round " + str(i + 1) + ": " + line)
print(" winner: " + options[r[1]])
winners = winners + [options[r[1]]]
print("Borda - " + plural(k - 1, "point") + " for first place, one less for each place below:")
points = count.borda(ballots, k)
line = ""
for i in ranked(points, k):
if line != "":
line = line + ", "
line = line + options[i] + " " + str(points[i])
print(" " + line)
top = count.leaders(points, k)
if len(top) == 1:
print(" winner: " + options[top[0]])
else:
print(" tie: " + names_text(options, top))
winners = winners + [names_text(options, top)]
print("Head to head - every pair of options, one against the other:")
wins = count.head_to_head(ballots, k)
for i in range(0, k - 2+1):
for j in range(i + 1, k):
if wins[i][j] > wins[j][i]:
print(" " + options[i] + " beats " + options[j] + " " + str(wins[i][j]) + " to " + str(wins[j][i]))
elif wins[j][i] > wins[i][j]:
print(" " + options[j] + " beats " + options[i] + " " + str(wins[j][i]) + " to " + str(wins[i][j]))
else:
print(" " + options[i] + " and " + options[j] + " tie " + str(wins[i][j]) + " to " + str(wins[j][i]))
w = count.beats_all(wins, k)
if w == 0 - 1:
print(" no option beats every other one")
winners = winners + ["none"]
else:
print(" winner: " + options[w] + ", who beats every other option")
winners = winners + [options[w]]
print("Winners: plurality " + winners[0] + "; instant runoff " + winners[1] + "; Borda " + winners[2] + "; head to head " + winners[3] + ".")
question = ""
options = []
ballots = []
running = True
while running:
print("")
print("== Poll ==")
print("1) new poll 2) vote 3) results 4) ballots 5) quit")
choice = text.trim(input("choice> "))
if choice == "1":
q = ask_text("question> ", 60)
if q == "":
print("Cancelled.")
else:
print("Options, one per line - 2 to " + str(most_options) + "; an empty line ends the list.")
new_options = []
while len(new_options) < most_options:
name = ask_text("option " + letters[len(new_options)] + "> ", 20)
if name == "":
break
clash = False
for o in new_options:
if text.upper(o) == text.upper(name):
clash = True
if clash:
print("That option is already there.")
else:
new_options = new_options + [name]
if len(new_options) < 2:
print("A poll needs at least two options; nothing changed.")
else:
question = q
options = new_options
ballots = []
listing = ""
for i in range(0, len(options)):
listing = listing + " " + letters[i] + ") " + options[i]
print("Poll ready: " + question)
print(listing)
elif choice == "2":
if len(options) == 0:
print("Set up a poll first.")
else:
print("Rank by letter, most preferred first (like " + letters[1] + " " + letters[0] + "), or put a count first for that many identical ballots (like 40 " + letters[0] + " " + letters[1] + "). An empty line ends voting.")
while True:
answer = text.trim(input("ballot> "))
if answer == "":
break
b = parse_ballot(answer, len(options))
if b == None:
print("Type letters from A to " + letters[len(options) - 1] + ", each once, with a count from 1 to " + str(most_at_once) + " in front if you like.")
else:
ballots = ballots + [b]
print("Counted " + plural(b[1], "ballot") + ": " + ranking_text(b[0]) + ".")
print(plural(count.total(ballots), "ballot") + " so far.")
elif choice == "3":
if count.total(ballots) == 0:
print("No ballots yet.")
else:
print("Question: " + question)
show_results(options, ballots)
elif choice == "4":
if count.total(ballots) == 0:
print("No ballots yet.")
else:
groups = []
for b in ballots:
merged = False
for g in groups:
if not merged and ranking_text(g[0]) == ranking_text(b[0]):
g[1] = g[1] + b[1]
merged = True
if not merged:
groups = groups + [[b[0], b[1]]]
print("")
print("-- ballots: " + plural(count.total(ballots), "ballot") + ", " + plural(len(groups), "different ranking") + " --")
for g in groups:
print("%6d" % g[1] + " " + ranking_text(g[0]))
elif choice == "5":
running = False
else:
print("Pick a number from 1 to 5.")
print("Bye.")
count.eml
eml# P019 poll - four ways to count the same ranked ballots. A ballot group is
# [ranking, count]: the ranking lists option numbers, most preferred first,
# and need not rank every option; count is how many identical ballots it
# stands for. Every rule that could tie says how the tie is broken.
def total(ballots):
0 => n
for b in ballots:
n + b[1] => n
return n
def first_choices(ballots, k, out_of):
# How many ballots put each of the k options first among those still in
# (out_of[i] True means option i is out). A ballot with nobody left is
# exhausted and counts for no one.
[] => votes
for i in [0:k - 1]:
votes + [0] => votes
for b in ballots:
0 - 1 => top
for o in b[0]:
if top == 0 - 1 and not out_of[o]:
o => top
if top != 0 - 1:
votes[top] + b[1] => votes[top]
return votes
def plurality(ballots, k):
[] => none_out
for i in [0:k - 1]:
none_out + [False] => none_out
return first_choices(ballots, k, none_out)
def runoff(ballots, k):
# Instant runoff: count first choices among the options still in; an
# option with more than half of the ballots still counting wins;
# otherwise the option with the fewest goes out and its ballots move to
# their next choice. A tie for fewest is broken by the fewest first
# choices in the first round, then by the option listed later. Returns
# [rounds, winner], a round being [votes, counting, out, gone]: out is
# the option that goes out (-1 in the round that has a winner) and gone[i]
# says whether option i was already out when the round was counted.
[] => out_of
for i in [0:k - 1]:
out_of + [False] => out_of
plurality(ballots, k) => first_round
[] => rounds
while True:
first_choices(ballots, k, out_of) => votes
0 => counting
0 => left
0 - 1 => best
for i in [0:k - 1]:
if not out_of[i]:
counting + votes[i] => counting
left + 1 => left
if best == 0 - 1 or votes[i] > votes[best]:
i => best
if 2 * votes[best] > counting or left == 1:
rounds + [[votes, counting, 0 - 1, [x for x in out_of]]] => rounds
return [rounds, best]
0 - 1 => worst
for i in [0:k - 1]:
if not out_of[i]:
if worst == 0 - 1 or votes[i] < votes[worst]:
i => worst
elif votes[i] == votes[worst] and first_round[i] <= first_round[worst]:
i => worst
rounds + [[votes, counting, worst, [x for x in out_of]]] => rounds
True => out_of[worst]
def borda(ballots, k):
# Borda: with k options, first place earns k - 1 points, second k - 2,
# and so on down to 0; an option a ballot leaves unranked earns 0.
[] => points
for i in [0:k - 1]:
points + [0] => points
for b in ballots:
for p in [0:len(b[0]) - 1]:
points[b[0][p]] + (k - 1 - p) * b[1] => points[b[0][p]]
return points
def prefers(ranking, i, j):
# Whether a ranking puts option i above option j (an unranked option is
# below every ranked one).
for o in ranking:
if o == i:
return True
if o == j:
return False
return False
def head_to_head(ballots, k):
# wins[i][j]: how many ballots prefer option i to option j.
[] => wins
for i in [0:k - 1]:
[] => row
for j in [0:k - 1]:
0 => n
if i != j:
for b in ballots:
if prefers(b[0], i, j):
n + b[1] => n
row + [n] => row
wins + [row] => wins
return wins
def beats_all(wins, k):
# The option that beats every other head to head, or -1 if there is none.
for i in [0:k - 1]:
True => all_beaten
for j in [0:k - 1]:
if i != j and wins[i][j] <= wins[j][i]:
False => all_beaten
if all_beaten:
return i
return 0 - 1
def leaders(scores, k):
# The options with the highest score, in option order.
0 => best
for i in [0:k - 1]:
if scores[i] > best:
scores[i] => best
[] => out
for i in [0:k - 1]:
if scores[i] == best:
out + [i] => out
return out
Python projection (count.py)
def total(ballots):
n = 0
for b in ballots:
n = n + b[1]
return n
def first_choices(ballots, k, out_of):
votes = []
for i in range(0, k):
votes = votes + [0]
for b in ballots:
top = 0 - 1
for o in b[0]:
if top == 0 - 1 and not out_of[o]:
top = o
if top != 0 - 1:
votes[top] = votes[top] + b[1]
return votes
def plurality(ballots, k):
none_out = []
for i in range(0, k):
none_out = none_out + [False]
return first_choices(ballots, k, none_out)
def runoff(ballots, k):
out_of = []
for i in range(0, k):
out_of = out_of + [False]
first_round = plurality(ballots, k)
rounds = []
while True:
votes = first_choices(ballots, k, out_of)
counting = 0
left = 0
best = 0 - 1
for i in range(0, k):
if not out_of[i]:
counting = counting + votes[i]
left = left + 1
if best == 0 - 1 or votes[i] > votes[best]:
best = i
if 2 * votes[best] > counting or left == 1:
rounds = rounds + [[votes, counting, 0 - 1, [x for x in out_of]]]
return [rounds, best]
worst = 0 - 1
for i in range(0, k):
if not out_of[i]:
if worst == 0 - 1 or votes[i] < votes[worst]:
worst = i
elif votes[i] == votes[worst] and first_round[i] <= first_round[worst]:
worst = i
rounds = rounds + [[votes, counting, worst, [x for x in out_of]]]
out_of[worst] = True
def borda(ballots, k):
points = []
for i in range(0, k):
points = points + [0]
for b in ballots:
for p in range(0, len(b[0])):
points[b[0][p]] = points[b[0][p]] + (k - 1 - p) * b[1]
return points
def prefers(ranking, i, j):
for o in ranking:
if o == i:
return True
if o == j:
return False
return False
def head_to_head(ballots, k):
wins = []
for i in range(0, k):
row = []
for j in range(0, k):
n = 0
if i != j:
for b in ballots:
if prefers(b[0], i, j):
n = n + b[1]
row = row + [n]
wins = wins + [row]
return wins
def beats_all(wins, k):
for i in range(0, k):
all_beaten = True
for j in range(0, k):
if i != j and wins[i][j] <= wins[j][i]:
all_beaten = False
if all_beaten:
return i
return 0 - 1
def leaders(scores, k):
best = 0
for i in range(0, k):
if scores[i] > best:
best = scores[i]
out = []
for i in range(0, k):
if scores[i] == best:
out = out + [i]
return out
text.eml
eml# P019 poll - reading what is typed. The interpreter that checks every
# session does not run string methods yet, so the text handling is written
# out here.
def trim(s):
# s without the spaces at either end.
0 => i
len(s) => j
while i < j and s[i] == " ":
i + 1 => i
while j > i and s[j - 1] == " ":
j - 1 => j
return s[i:j]
def upper(s):
# s with a-z turned into A-Z; everything else as it was.
"abcdefghijklmnopqrstuvwxyz" => lower_letters
"ABCDEFGHIJKLMNOPQRSTUVWXYZ" => upper_letters
"" => out
for c in s:
c => d
for i in [0:25]:
if lower_letters[i] == c:
upper_letters[i] => d
out + d => out
return out
def number(s):
# The value of s if it is digits only (at least one), otherwise -1.
if s == "":
return 0 - 1
0 => n
for c in s:
if not (c in "0123456789"):
return 0 - 1
n * 10 + int(c) => n
return n
def words(s):
# The words of s, split at spaces and commas.
[] => out
"" => word
for c in s:
if c == " " or c == ",":
if word != "":
out + [word] => out
"" => word
else:
word + c => word
if word != "":
out + [word] => out
return out
def tenths(n, d):
# n / d to one decimal, rounded half up, as text: 2 / 3 is "0.7".
2 * 10 * n + d => t
int((t - t % (2 * d)) / (2 * d)) => v
return str(int((v - v % 10) / 10)) + "." + str(v % 10)
Python projection (text.py)
def trim(s):
i = 0
j = len(s)
while i < j and s[i] == " ":
i = i + 1
while j > i and s[j - 1] == " ":
j = j - 1
return s[i:j]
def upper(s):
lower_letters = "abcdefghijklmnopqrstuvwxyz"
upper_letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
out = ""
for c in s:
d = c
for i in range(0, 26):
if lower_letters[i] == c:
d = upper_letters[i]
out = out + d
return out
def number(s):
if s == "":
return 0 - 1
n = 0
for c in s:
if not c in "0123456789":
return 0 - 1
n = n * 10 + int(c)
return n
def words(s):
out = []
word = ""
for c in s:
if c == " " or c == ",":
if word != "":
out = out + [word]
word = ""
else:
word = word + c
if word != "":
out = out + [word]
return out
def tenths(n, d):
t = 2 * 10 * n + d
v = int((t - t % (2 * d)) / (2 * d))
return str(int((v - v % 10) / 10)) + "." + str(v % 10)