Next quiz is posted as code snippet. It is quite interesting code. What it does? And where in your system you already have this code? (in little different format) (If you have not follow tip in page http://python.org/download/)
Quiz of the week: Where in your system you have this code?
class LazyList:
def __init__(self, g):
self.sofar = []
self.fetch = g.next
def __getitem__(self, i):
sofar, fetch = self.sofar, self.fetch
while i >= len(sofar):
sofar.append(fetch())
return sofar[i]
def times(n, g):
for i in g:
yield n * i
def merge(g, h):
ng = g.next()
nh = h.next()
while 1:
if ng < nh:
yield ng
ng = g.next()
elif ng > nh:
yield nh
nh = h.next()
else:
yield ng
ng = g.next()
nh = h.next()
def m235():
yield 1
# Gack: m235 below actually refers to a LazyList.
me_times2 = times(2, m235)
me_times3 = times(3, m235)
me_times5 = times(5, m235)
for i in merge(merge(me_times2,
me_times3),
me_times5):
yield i
#Print as many of these as you like -- *this* implementation is memory-
#efficient.
if __name__ == '__main__':
m235 = LazyList(m235())
for i in range(5):
print [m235[j] for j in range(15*i, 15*(i+1))]
TrustyTony 888 ex-Moderator Team Colleague Featured Poster
Interestingly you also got it if you have OpenOffice.org 3 or pypy installed, even Qt 2010.05 and QtSDK seems to have it in pythongdb.
TrustyTony 888 ex-Moderator Team Colleague Featured Poster
My version of code (would like to change to __iter__ but was little complicated to change):
""" Generating Hamming sequence having only factors 2,3 or 5
version with for in LazyList and using heapq.merge
http://oeis.org/A051037
m235 is indexed from zero Python style
original code from: <Python installation directory>/Lib/test/test_generators.py
"""
import heapq
class LazyList:
def __init__(self, g):
self.sofar, self.fetch = [], g.next
def __getitem__(self, index):
for c in range(len(self.sofar), index + 1):
self.sofar.append(self.fetch())
return self.sofar[index]
def times(n, g):
for i in g:
yield n * i
def m235():
yield 1
previous = 1
for val in heapq.merge(times(2, m235), times(3, m235), times(5, m235)):
if val != previous:
previous = val
yield val
m235 = LazyList(m235())
if __name__ == '__main__':
perline, max_length, linecount = 6, 10, 150
format = "%%%ii" % max_length
for count in range(linecount):
print(', '.join(format % m235[index]
for index in range(perline * count, perline * (count + 1))) +
(',' if count != linecount - 1 else '.'))Worthy to check the test files otherwise as this same file has for example code for Knigth's Tour also.
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