# HG changeset patch
# User paulb
# Date 1127771956 0
# Node ID c64efeb60986c16c790e355a37b096dee5cd74ff
# Parent  d5bb6c75e31fdce6ceecc313859a2cf53464d190
[project @ 2005-09-26 21:59:16 by paulb]
Added a text indexing demonstration using a simple implementation of an
indexer along with an example which uses message exchanges to coordinate
communications between the parent and child processes.

diff -r d5bb6c75e31f -r c64efeb60986 tests/Dict.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/Dict.py	Mon Sep 26 21:59:16 2005 +0000
@@ -0,0 +1,91 @@
+#!/usr/bin/env python
+
+"A simple file indexer."
+
+import codecs
+
+class Indexer:
+    def __init__(self, dict_location, encoding=None):
+        self.dict_location = dict_location
+        self.encoding = encoding
+
+        # Initialisation.
+
+        self.index = self.make_index()
+
+    def get_index(self):
+        return self.index
+
+    def make_index(self):
+
+        "Return a dictionary containing an index structure for the dict."
+
+        if self.encoding is None:
+            f = open(self.dict_location)
+        else:
+            f = codecs.open(self.dict_location, encoding=self.encoding)
+        s = f.read()
+        f.close()
+
+        tokens = s.split()
+        index = {}
+
+        for token in tokens:
+            slot = index
+            for c in token:
+                if not slot.has_key(c):
+                    slot[c] = {}, []
+                slot, words = slot[c]
+
+            if token not in words:
+                words.append(token)
+
+        return index
+
+class Searcher:
+    def __init__(self, index):
+        self.index = index
+
+    def find(self, pattern):
+
+        "Find words beginning with the given 'pattern'."
+
+        slot = self.index
+        words = []
+
+        for c in pattern:
+            if not slot.has_key(c):
+                return []
+            slot, words = slot[c]
+
+        results = []
+        results += words
+        results += self.get_all_words(slot)
+        return results
+
+    def get_all_words(self, slot):
+
+        "Get all words under the given index 'slot'."
+
+        all_words = []
+        keys = slot.keys()
+        keys.sort()
+        for c in keys:
+            this_slot, words = slot[c]
+            all_words += words
+            all_words += self.get_all_words(this_slot)
+        return all_words
+
+def update(index1, index2):
+    for key in index2.keys():
+        if not index1.has_key(key):
+            index1[key] = index2[key]
+        else:
+            slot1, words1 = index1[key]
+            slot2, words2 = index2[key]
+            for word in words2:
+                if not word in words1:
+                    words1.append(word)
+            update(slot1, slot2)
+
+# vim: tabstop=4 expandtab shiftwidth=4
diff -r d5bb6c75e31f -r c64efeb60986 tests/start_indexer.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/start_indexer.py	Mon Sep 26 21:59:16 2005 +0000
@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+
+from parallel import start, Exchange
+from Dict import Indexer, Searcher, update
+
+def apply_indexer(channel, filename):
+    print "Indexing", filename
+    indexer = Indexer(filename)
+    channel.send(indexer.get_index())
+
+def get_searcher(filenames):
+    master_index = {}
+
+    # Start indexing.
+
+    channels = []
+    for filename in filenames:
+        channels.append(start(apply_indexer, filename))
+
+    # Start listening for responses.
+
+    exchange = Exchange(channels)
+    while len(channels) > 0:
+        print "Waiting for %d channels..." % len(channels)
+        for channel in exchange.ready():
+            index = channel.receive()
+            update(master_index, index)
+            channels.remove(channel)
+
+    # Provide a search interface.
+
+    return Searcher(master_index)
+
+if __name__ == "__main__":
+    import sys
+    filenames = sys.argv[1:]
+    searcher = get_searcher(filenames)
+    while 1:
+        print "Pattern:",
+        pattern = raw_input()
+        print searcher.find(pattern)
+
+# vim: tabstop=4 expandtab shiftwidth=4