list Comprehension Example

# see http://stackoverflow.com/questions/6722985/fastest-way-in-python-to-find-a-startswith-substring-in-a-long-sorted-list-of-s
## http://pastebin.com/sCd4424k
import random
import time
import string
from bisect import bisect_left

WORDLIST_FILENAME = "words.txt"

def load_words():
    """
    Returns a list of valid words. Words are strings of lowercase letters.
    
    Depending on the size of the word list, this function may
    take a while to finish.
    """
    print "Loading word list from file..."
    # inFile: file
    inFile = open(WORDLIST_FILENAME, 'r', 0)
    # wordlist: list of strings
    wordlist = []
    for line in inFile:
        wordlist.append(line.strip().lower())
    print "  ", len(wordlist), "words loaded."
    return wordlist

def frag_wordexists_Peter_simple(wordlist, word_fragment): 
    return any(w.startswith(word_fragment) for w in wordlist)

def frag_wordexists_Peter_bisect_left(wordlist, word_fragment):
    try:
        return wordlist[bisect_left(wordlist, word_fragment)].startswith(word_fragment)
    except IndexError:
        return False # word_fragment is greater than all entries in wordlist

def trim_list_comprehension(wordlist, word_fragment):
    """returns the wordlist containing only words starting with 'word_fragment'"""
    wordlist = [w for w in wordlist if w.startswith(word_fragment)]
    return wordlist

def trim_bisect(wordlist, word_fragment):
    """returns the wordlist containing only words starting with 'word_fragment'"""
    wordlist[bisect_left(wordlist, word_fragment):
         bisect_left(wordlist, word_fragment[:-1] + chr(ord(word_fragment[-1])+1))]
    return wordlist

# Actually load the dictionary of words and point to it with 
# the wordlist variable so that it can be accessed from anywhere
# in the program.
wordlist = load_words()
trimwordlist_comprehension = wordlist[:]
trimwordlist_bisect = wordlist[:]
peter_simple_total = peter_bisect_total = trim_comp_total = trim_bisect_total = 0

for word_fragment in ("p", "py", "pyt", "pyth", "pytho"):
    print "Testing '" + word_fragment + "' with Peter's simple test"
    start = time.time()
    if frag_wordexists_Peter_simple(wordlist, word_fragment):
        runtime = time.time() - start
        print runtime
        peter_simple_total += runtime

print "Testing '" + word_fragment + "' with Peter's bisect left test"
    start = time.time()
    if frag_wordexists_Peter_bisect_left(wordlist, word_fragment):
        runtime = time.time() - start
        print runtime
        peter_bisect_total += runtime

print "Testing '" + word_fragment + "' with trimming the list using a list comprehension"
    start = time.time()
    trimwordlist_comprehension = trim_list_comprehension(trimwordlist_comprehension, word_fragment)
    if len(trimwordlist_comprehension):
        runtime = time.time() - start
        print runtime
        trim_comp_total += runtime

print "Testing '" + word_fragment + "' with trimming the list using Neil G's bisect"
    start = time.time()
    trimwordlist_bisect = trim_bisect(trimwordlist_bisect, word_fragment)
    if len(trimwordlist_bisect):
        runtime = time.time() - start
        print runtime
        trim_bisect_total += runtime

print ""
print 'The totals for all strings "p", "py", "pyt", "pyth", "pytho" are as follows:'
print "In total, Peter's simple test took " + str(peter_simple_total)
print "In total, Peter's bisect left test took " + str(peter_bisect_total)
print "In total, the list comprehension took " + str(trim_comp_total)
print "In total, Neil G's bisect took " + str(trim_bisect_total)

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