473,574 Members | 2,498 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

need help on generator... (re)

Joh
hello,

thanks to all who replied to my post (2005-01-21) - (i can not post
inside the original thread as i get "Unable to retrieve message
cs************* @news.t-online.com" from googlenews :(
Do you mean:
[1,2], [2,3], [3,4], [1,2,3], [2,3,4], [1,3,4]
(E.g. all elements in the power set except the empty set, the sets with
one element and the sets with all elements.)
Otherwise, please describe your desired sets in verbal - I cannot see
the point.
yes it was my wishes, but having the others empty, one and all
elements wasn't a big trouble, actually i wanted to understand more
generators.
Here is an (untested) variant that accepts any iterable while trying to
remain memory-efficient. This makes it necessary to shuffle the order of
the output a bit. from itertools import tee, islice def gen(iterable, start, end):
it = iter(iterable)
while True:
it, a = tee(it)
a = tuple(islice(a, end-1))
for sz in xrange(start, len(a)+1):
yield a[:sz]
it.next()

if __name__ == "__main__":
print list(gen(range( 1, 5), 2, 4))


please, this one looks interesting, could you explain a bit how it
works and why it "remain memory-efficient" ?

thanks,
Jul 18 '05 #1
1 1276
Joh wrote:
def gen(iterable, start, end):
it*=*iter(ite rable)
while*True:
it,*a*=*tee(i t)
a*=*tuple(isl ice(a,*end-1))
for*sz*in*xra nge(start,*len( a)+1):
yield*a[:sz]
it.next()

if __name__ == "__main__":
print*list(ge n(range(1,*5),* 2,*4))


please, this one looks interesting, could you explain a bit how it
works and why it "remain memory-efficient" ?


If you have a generator of the form

def gen1(iterable):
for i in iterable:
yield f(i)
for i in iterable:
yield g(i)

and then use it

for item in gen1(range(huge _number)):
do_something_us eful_with(item)

it will only work when you feed it with something you can iterate over
multiple times, e. g. a list, not a generator that reads data on every call
of the next() method. That means you must store the data for (to keep it
simple) the lifetime of gen1(). If you can modify the generator to

def gen2(iterable):
for i in iterable:
yield f(i)
yield g(i)

for item in gen2(xrange(hug e_number)): # switched from range() to xrange()
do_something_us eful_with(item)

there is no such restriction to the iterable. All data can be read,
processed and garbage-collected immediately.

The gen() generator is a bit more complex in that it has to store a few
adjacent items instead of only one and allows for an arbitrary number of
functions (inlined as yield of an n-tuple) instead of always two functions,
but the idea is the same.

Peter


Jul 18 '05 #2

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

4
2320
by: Wai Yip Tung | last post by:
I'm attempting to turn some process than uses callback to return result into a more user friendly generator. I'm hitting some road block so any pointer would be appriciated. Let say there is an existing method producer(x, cb). It calls the supplied cb() every time when there is data available. The definititon of cb should be: def cb(data)
45
2996
by: Joh | last post by:
hello, i'm trying to understand how i could build following consecutive sets from a root one using generator : l = would like to produce : , , , ,
12
1932
by: Thomas Lotze | last post by:
Hi, I'm trying to figure out what is the most pythonic way to interact with a generator. The task I'm trying to accomplish is writing a PDF tokenizer, and I want to implement it as a Python generator. Suppose all the ugly details of toknizing PDF can be handled (such as embedded streams of arbitrary binary content). There remains one...
0
3000
by: Limpor | last post by:
Hello, I am new to learning java, and i am trying to build the class for a calculation card game, unfortunately i can't get the public Card top() and Card takeTop() method in the Stock class. Can someone helps me. Thanks!! ----------------------------------------------------------------------- The code for the Stock class:...
0
2827
by: Limpor | last post by:
Hi, I’m working on a solitaire game as my course assignment, and I am having trouble to dealing with Stock class, which consists of an upturned top card plus deck. The code for Stock class: import java.util.*; import java.awt.*; /** * The Stock is the deck of unused cards. It is subtly different from the deck * itself in several ways....
2
2716
by: Bernhard Mulder | last post by:
I have something like the following (using Python 2.5 syntax): class adapt(object): def __init__(self): self.iterator = self.generator() self.n = 0 def generator(self): while True: while True:
1
1643
by: Schüle Daniel | last post by:
Hello, I came up with this algorithm to generate all permutations it's not the best one, but it's easy enough # lst = list with objects def permute3(lst): tmp = lenlst = len(lst) def permute(perm, level):
4
1631
by: UMstudent | last post by:
I'm working on this program for class where I have to an amount of numbers that are randomly picked from 0 - 50. So what I have done is say there are 20 slots in my array so I'm trying to generator 20 random numbers for the array between 0-50 however I've ran into a few problems. Mainly figuring out how to make it print 20 seperate completely...
2
11103
by: masker | last post by:
I was on the web trying to find a javascript that would allow me to input a number on my website and have it increase by a given percentage every second. During my search I found the Earth Population Calculator on the javascripkit.com site. The Calculator functions just as I imagine I want my number generator to function, but I need it to...
5
11553
by: byahne | last post by:
We just went live today with a production SQL Server 2005 database running with our custom Java application. We are utilizing the jTDS open source driver. We migrated our existing application which was using InterBase over to SQL Server. To minimize the impact to our code, we created a stored procedure which would allow us to manage our...
0
8225
jinu1996
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that...
1
7800
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For...
0
8092
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the...
0
6437
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then...
1
5610
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes...
0
5296
by: conductexam | last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one. At the time of converting from word file to html my equations which are in the word document file was convert...
0
3738
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in...
1
2230
by: 6302768590 | last post by:
Hai team i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
0
1051
bsmnconsultancy
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.