added summarization code for lists of Congresses, for later display on politician search pages

Author: kragen

webapp.py

@@ -1,4 +1,5 @@
 #!/usr/bin/env python
+# -*- coding: utf-8 -*-
 import re, sys
 import web
 
@@ -685,6 +686,67 @@ def notfound():
 def internalerror():
     return web.internalerror(file('templates/500.html').read())
 
+def and_join(phrases):
+    """Format a list of phrases as an English list.
+
+    This must already exist in web.py but I can't find it."""
+    phrases = list(phrases)
+    assert len(phrases) > 0          # caller should special-case this
+    if len(phrases) == 1:
+        return phrases[0]
+    elif len(phrases) == 2:
+        return ' and '.join(phrases)
+    else:
+        return ', '.join(phrases[:-1] + ['and ' + phrases[-1]])
+
+def pluralize(noun, plural, number):
+    """Inflect a noun for number."""
+    if number == 1:
+        return noun
+    else:
+        return plural
+
+def divide_into_ranges(ints):
+    """Summarize a sorted sequence of ints as a sequence of contiguous ranges.
+
+    Return value is a list of lists of the form `[start, stop]`, where `stop`
+    is one more than the last item in the range.
+    """
+    rv = []
+
+    for item in ints:
+        if len(rv) == 0:
+            rv.append([item, item+1])
+        elif item == rv[-1][1]:
+            rv[-1][1] += 1
+        else:
+            rv.append([item, item+1])
+
+    return rv
+
+def congress_ranges(congresses):
+    """Format a list of Congress ordinal numbers
+    as a coalesced English sequence of ranges."""
+
+    nthstr = web.utils.nthstr
+
+    if not congresses:
+        return "no known Congresses"
+
+    ranges = divide_into_ranges(congresses)
+    phrases = []
+    for start, stop in ranges:
+        if stop == start + 1:
+            phrases.append(nthstr(start))
+        elif stop == start + 2:
+            phrases.append(nthstr(start))
+            phrases.append(nthstr(start+1))
+        else:
+            phrases.append('%s–%s' % (nthstr(start), nthstr(stop-1)))
+
+    return "the %s %s" % (and_join(phrases),
+                          pluralize("Congress", "Congresses", len(congresses)))
+
 app.notfound = notfound
 if production_mode:
     app.internalerror = web.emailerrors(config.send_errors_to, internalerror)

webapp_test.py

@@ -239,6 +239,26 @@ def test_dproperty():
 def test_blog():
     html('/blog/')
 
+def test_congress_ranges():
+    ok(webapp.pluralize('Congress', 'Congresses', 0),  'Congresses')
+    ok(webapp.pluralize('Congress', 'Congresses', 1),  'Congress')
+    ok(webapp.pluralize('Congress', 'Congresses', 2),  'Congresses')
+    ok(webapp.pluralize('Congress', 'Congresses', 20), 'Congresses')
+
+    ok(webapp.congress_ranges([]), "no known Congresses")
+    ok(webapp.congress_ranges([104]), "the 104th Congress")
+    ok(webapp.congress_ranges([102]), "the 102nd Congress")
+    ok(webapp.congress_ranges([102, 103]), "the 102nd and 103rd Congresses")
+    ok(webapp.congress_ranges([102, 104, 105]),
+       "the 102nd, 104th, and 105th Congresses")
+    ok(webapp.congress_ranges([100, 102, 104, 105]),
+       "the 100th, 102nd, 104th, and 105th Congresses")
+    ok(webapp.congress_ranges([102, 103, 104]), "the 102nd–104th Congresses")
+    ok(webapp.congress_ranges([86, 87, 88, 90, 91, 92]),
+       "the 86th–88th and 90th–92nd Congresses")
+    ok(webapp.congress_ranges([86, 87, 88, 90, 91, 92, 94, 95, 96]),
+       "the 86th–88th, 90th–92nd, and 94th–96th Congresses")
+
 def test_webapp():
     "Test the actual watchdog.net webapp.app app."
     test_state()
@@ -249,6 +269,7 @@ def test_webapp():
     test_find()                         # slow
 
 def main():
+    test_congress_ranges()
     test_webapp()