[Tutor] Creating a unicode string from bytes and % opperator

[Wesley Brooks]

Dear Users,

I'm trying to create a unicode character from two bytes. Unfortunatly
I'm getting a "UnicodeDecodeError". Can some one please suggest an
alternative way of doing what's bellow? In the example bellow the two
bytes have been converted into a string hex value, but they could just
as easily be an integer or binary value if either is easier to deal
with.

Python 2.4.3 - Enthought Edition 1.0.0 (#69, Aug  2 2006, 12:09:59) [MSC v.1310
32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> a = u"\u%s%s" %('0d', 'fe')
UnicodeDecodeError: 'unicodeescape' codec can't decode bytes in position 0-2: tr
uncated \u escape
>>>

Cheers,

Wesley Brooks.
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Re: [Tutor] Creating a unicode string from bytes and % opperator

[Tim Golden]

Wesley Brooks wrote:

I'm trying to create a unicode character from two bytes. Unfortunatly
I'm getting a "UnicodeDecodeError". Can some one please suggest an
alternative way of doing what's bellow? In the example bellow the two
bytes have been converted into a string hex value, but they could just
as easily be an integer or binary value if either is easier to deal
with.

Python 2.4.3 - Enthought Edition 1.0.0 (#69, Aug  2 2006, 12:09:59) [MSC v.1310
32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.

a = u"\u%s%s" %('0d', 'fe')

UnicodeDecodeError: 'unicodeescape' codec can't decode bytes in position 0-2: tr
uncated \u escape


Nice try :)

Unfortunately, if you think about what's happening here, the
"string interpreter" bit of Python is getting to that
unicode-escape before the "%-processing" bit of Python.
So Python's trying --and failing-- to interpret \u%s%s as some sort of
bizarre unicode escape.

Can you not just use the unichr function?

TJG
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Re: [Tutor] Creating a unicode string from bytes and % opperator

[Wesley Brooks]

Thanks Tim Golden,

That'll do the trick! Thought there must have been something simple for it!

Cheers,

Wesley Brooks

2008/7/28 Tim Golden <[EMAIL PROTECTED]>:
> Wesley Brooks wrote:
>>
>> I'm trying to create a unicode character from two bytes. Unfortunatly
>> I'm getting a "UnicodeDecodeError". Can some one please suggest an
>> alternative way of doing what's bellow? In the example bellow the two
>> bytes have been converted into a string hex value, but they could just
>> as easily be an integer or binary value if either is easier to deal
>> with.
>>
>> Python 2.4.3 - Enthought Edition 1.0.0 (#69, Aug  2 2006, 12:09:59) [MSC
>> v.1310
>> 32 bit (Intel)] on win32
>> Type "help", "copyright", "credits" or "license" for more information.
>
> a = u"\u%s%s" %('0d', 'fe')
>>
>> UnicodeDecodeError: 'unicodeescape' codec can't decode bytes in position
>> 0-2: tr
>> uncated \u escape
>
> Nice try :)
>
> Unfortunately, if you think about what's happening here, the
> "string interpreter" bit of Python is getting to that
> unicode-escape before the "%-processing" bit of Python.
> So Python's trying --and failing-- to interpret \u%s%s as some sort of
> bizarre unicode escape.
>
> Can you not just use the unichr function?
>
> TJG
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Re: [Tutor] Creating a unicode string from bytes and % opperator

[Tim Golden]

Wesley Brooks wrote:

Thanks Tim Golden,

That'll do the trick! Thought there must have been something simple for it!


To be perverse, you *could* have done it like this:

eval ("u'\u" + "%s%s'" % ("0d", "fe"))

But please don't :)

TJG
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Re: [Tutor] Online class/education for Python?

[bhaaluu]

On Sun, Jul 27, 2008 at 12:13 PM, Dick Moores <[EMAIL PROTECTED]> wrote:
> At 07:18 AM 7/27/2008, bhaaluu wrote:
>
>> So if
>> a student goes through PPftAB2E, and wants to continue programming games,
>> I'd recommend "Game Programming" by Andy Harris [ISBN-13:
>> 978-0-470-06822-9].
>> Game Programming is a fairly complete PyGame tutorial.
>
> What do you think of _Beginning Game Development with Python and Pygame_,
> Apress, 2007?
>
> Dick Moores

The main difference between GAME PROGRAMMING and BEGINNING GAME DEVELOPMENT
is that the former deals with 2D scrolling arcade type games, using
PyGame; and the
latter gets into 3D games using PyGame and openGL (I think). I don't
have the McGugan
book, so I don't know for sure. You can take a look at a sample
chapter at Will's site:
http://www.willmcgugan.com/2007/10/04/free-chapter-of-beginning-game-development-with-python-and-pygame/
The publisher also has the source code from the book available.

Happy Programming!
-- 
b h a a l u u at g m a i l dot c o m
Kid on Bus: What are you gonna do today, Napoleon?
Napoleon Dynamite: Whatever I feel like I wanna do. Gosh!
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[Tutor] Memory error - how to manage large data sets?

[Karthik]

Hi,

 

I am new to Python programming, I was trying to work out a few problems in
order to grasp the knowledge gained after going through the basic chapters
on Python programming. I got stuck with a memory error.

 

Following is what I did,

 

1. I need to find the sum of all numbers at even positions in the
Fibonacci series upto 2 million.

2. I have used lists to achieve this.

3. My program works good with smaller ranges. Say till 10,000 or even
100,000. However when I compute the sum for bigger ranges it gives me the
memory error.

4. Also could someone tell me how to get the result in the form of an
exponent. For instance, I would prefer 10^5 rather  10.

 

Thanks in advance,

Karthik

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Re: [Tutor] Memory error - how to manage large data sets?

[Alan Gauld]

"Karthik" <[EMAIL PROTECTED]> wrote


I am new to Python programming, I was trying to work out a few 
problems in
order to grasp the knowledge gained after going through the basic 
chapters

on Python programming. I got stuck with a memory error.


Always show us the full error text, it contains a lot of useful data.

It is usually helpful to show us the code too if not too long.
Alternatively post in on a web site such as pastebin.


Following is what I did,
1. I need to find the sum of all numbers at even positions in 
the

Fibonacci series upto 2 million.


Shouldn't be a problem.


2. I have used lists to achieve this.


One list should suffice. (and you could do it without any lists...)

3. My program works good with smaller ranges. Say till 10,000 or 
even
100,000. However when I compute the sum for bigger ranges it gives 
me the

memory error.

4. Also could someone tell me how to get the result in the form 
of an

exponent. For instance, I would prefer 10^5 rather  10.


You can use string formatting using the %e or %g markers.
See my tutorial topic Simple Sequences for more info on format strings
or search the documentation.

--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld 



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Re: [Tutor] Memory error - how to manage large data sets?

[Karthik]

Forgot to include the following information,

 

Platform - win32

Version - 2.5.1

 

Error message:

 

Traceback (most recent call last):

  File "C:\Python25\programs\fibo.py", line 10, in 

if i % 2 == 0:

MemoryError

 

Code:

 

fib = []

even = []

def fibonacci(x,y):

return x+y

for i in range (0,100):

if i < 2:

fib.append(i)

else:

i = fib[i-1] + fib[i-2]

if i % 2 == 0:

fib.append(i)

even.append(i)

else:

fib.append(i)

total = reduce(fibonacci,even)

print total

 

Any pointers would be of great help to me.

 

Regards,

Karthik

 

From: Karthik [mailto:[EMAIL PROTECTED] 
Sent: Monday, July 28, 2008 9:27 PM
To: 'tutor@python.org'
Subject: Memory error - how to manage large data sets?

 

Hi,

 

I am new to Python programming, I was trying to work out a few problems in
order to grasp the knowledge gained after going through the basic chapters
on Python programming. I got stuck with a memory error.

 

Following is what I did,

 

1. I need to find the sum of all numbers at even positions in the
Fibonacci series upto 2 million.

2. I have used lists to achieve this.

3. My program works good with smaller ranges. Say till 10,000 or even
100,000. However when I compute the sum for bigger ranges it gives me the
memory error.

4. Also could someone tell me how to get the result in the form of an
exponent. For instance, I would prefer 10^5 rather  10.

 

Thanks in advance,

Karthik

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Re: [Tutor] Memory error - how to manage large data sets?

[Chris Fuller]

On Monday 28 July 2008 10:56, Karthik wrote:
> Hi,
>
>
>
> I am new to Python programming, I was trying to work out a few problems in
> order to grasp the knowledge gained after going through the basic chapters
> on Python programming. I got stuck with a memory error.
>
>
>
> Following is what I did,
>
>
>
> 1. I need to find the sum of all numbers at even positions in the
> Fibonacci series upto 2 million.
>
> 2. I have used lists to achieve this.
>
> 3. My program works good with smaller ranges. Say till 10,000 or even
> 100,000. However when I compute the sum for bigger ranges it gives me the
> memory error.
>
> 4. Also could someone tell me how to get the result in the form of an
> exponent. For instance, I would prefer 10^5 rather  10.
>
>
>
> Thanks in advance,
>
> Karthik

It sounds like you are storing all the fibonacci numbers as you generate them.  
Why?  You only need the previous two to find the next in the sequence.  The 
sum is a single number that you can add every other element in the sequence 
to.  You only need to store three numbers in memory.  Storing millions is 
wasteful, and doesn't scale very well.

To find an exponent, use the "**" operator.  For instance, 2**3 is 8, and 3**2 
is 9.

Cheers
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Re: [Tutor] Memory error - how to manage large data sets?

[Danny Yoo]

> 1. I need to find the sum of all numbers at even positions in the
> Fibonacci series upto 2 million.
>
> 2. I have used lists to achieve this.

I see.  You may want to produce a "sequence" or "iterator" of
fibonacci numbers rather than an explicit list.  As it is, your
machine does not have enough physical memory to hold the whole
sequence at once.

Python has a "generator" language feature that supports a style of
programming on infinite sequences.  You can find an introduction to
Python generators here:

http://linuxgazette.net/100/pramode.html
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Re: [Tutor] Memory error - how to manage large data sets?

[Daniel Sarmiento]

Hi

I tried to run your code and checked (with top) the memory ussage and
it uses more than 2 Gb of memory.

I tried to modify the code a little bit to use less memory and came up
with this:

fib = {0:0,1:1}
even = []

def fibonacci(x,y):
   return x+y

for j in xrange (2,100):
i = fib[j-1] + fib[j-2]
if i % 2 == 0:
even.append(i)
fib = {j-1:fib[j-1], j:i}

total = reduce(fibonacci,even)
print total

First, I replaced range with xrange.
I figured that you only need the last two values in the fibonnaci
series to calculate the next value, so I replaced the fib list with a
dictionary to only store the last two values instead of the whole
series.

It looks like the progam still hangs and I did not notice any memory
imrovements when running it with 1 000 000

Am I wrong thinking that the modifications I made help use less memory?

> Date: Mon, 28 Jul 2008 22:44:08 +0530
> From: "Karthik" <[EMAIL PROTECTED]>
> Subject: Re: [Tutor] Memory error - how to manage large data sets?
> To: 
> Message-ID: <[EMAIL PROTECTED]>
> Content-Type: text/plain; charset="us-ascii"
>
> Forgot to include the following information,
>
>
>
> Platform - win32
>
> Version - 2.5.1
>
>
>
> Error message:
>
>
>
> Traceback (most recent call last):
>
>  File "C:\Python25\programs\fibo.py", line 10, in 
>
>if i % 2 == 0:
>
> MemoryError
>
>
>
> Code:
>
>
>
> fib = []
>
> even = []
>
> def fibonacci(x,y):
>
>return x+y
>
> for i in range (0,100):
>
>if i < 2:
>
>fib.append(i)
>
>else:
>
>i = fib[i-1] + fib[i-2]
>
>if i % 2 == 0:
>
>fib.append(i)
>
>even.append(i)
>
>else:
>
>fib.append(i)
>
> total = reduce(fibonacci,even)
>
> print total
>
>
>
> Any pointers would be of great help to me.
>
>
>
> Regards,
>
> Karthik
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[Tutor] Turtle problem: how to exit the .exe?

[Dick Moores]

Win XP, Python 2.51

The script is at   It 
calls the Windows console to show the printed data.


I've successfully used PyInstaller to make an .exe for this.  For 
informed users, exiting the program before it finishes is easily and 
cleanly done by a Ctrl+Q on the console window.


But I'd like to make a version of the script that doesn't report any 
data. How can I write it so that the .exe can be easily exited by the 
user? If Tkinter instead of Turtle were involved, I could have an 
Exit button connected to command=root.quit .


Thanks,

Dick Moores

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[Tutor] login using PAM

[johnf]

I have been attempting to research the web on how python-pam works.  Does 
anyone have example code?
-- 
John Fabiani
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Re: [Tutor] Unable to Reconfigure IDLE

[Thomas Corbett]

On Jul 27, 2008, at 7:16 AM, Tim Golden wrote:


Thomas Corbett wrote:

On Jul 26, 2008, at 9:02 AM, Alan Gauld wrote:


"Thomas Corbett" <[EMAIL PROTECTED]> wrote

Configured shell window to wrong size, now can't seem to find the  
menu  (Options > Configure) to resize the shell.


Don't you just resize it then close it and the next time it opens
it uses the new size?

Thats how I thought it was supposed to work!

Alan G

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The window is too large to resize.


I missed the beginning of this thread, but I assume that you
mean its edges are off the visible screen so you can't use
the mouse to grab the frame and resize it? If so, and if
you're on Windows, you can resize with the keyboard:
Alt-Space S will put you in Sizing mode; then use the
cursor keys to move the edges in and out. Alternatively,
Alt -Space M will put the window in Moving mode and, again,
the cursor keys can be used to bring a corner into view
and into range of the mouse.

TJG

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Running IDLE 1.2.2 under MacPython 2.5 on Mac OS X 5.1. Not aware of a  
similar option on Mac.


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Re: [Tutor] Turtle problem: how to exit the .exe?

[Alan Gauld]

"Dick Moores" <[EMAIL PROTECTED]> wrote

But I'd like to make a version of the script that doesn't report any 
data. How can I write it so that the .exe can be easily exited by 
the user? If Tkinter instead of Turtle were involved, I could have 
an Exit button connected to command=root.quit .


Tkinter is involved, turtle usesw Tkinter.

But to exit I would expect the standard Windows exit key
combination (Alt F4) to work fine?

Alan G 



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Re: [Tutor] Memory error - how to manage large data sets?

[Alan Gauld]

"Karthik" <[EMAIL PROTECTED]> wrote in message 
news:[EMAIL PROTECTED]

Forgot to include the following information,
Platform - win32
Version - 2.5.1
Error message:
Traceback (most recent call last):
 File "C:\Python25\programs\fibo.py", line 10, in 
   if i % 2 == 0:
MemoryError


OK, It does look like you bust your memory allocation.


Code:



fib = []
even = []


You don't really need two lists.


def fibonacci(x,y):
   return x+y


And this isn't really the fibonacci function its an addition
which you don;t need(see below)


for i in range (0,100):


This creates a 3rd list of 1 million numbers, so thats
3 million * the storage of one number. Still not enough
to trouble most PCs nowadays...


   if i < 2:
   fib.append(i)
   else:
   i = fib[i-1] + fib[i-2]
   if i % 2 == 0:
   fib.append(i)


You want to append to fib on every number not just on evens?
So just take this outside the if.


   even.append(i)


You don't need this because we can extract the even numbers
when we do the summation later. All its doing it gobbling up space.


   else:
   fib.append(i)


dispense with the else and just put the fib append outside.
ie your code becomes

for i in xrange (0,100):  # xranmge should avoid the extra list
   if i >= 2:
   i = fib[i-1] + fib[i-2]
   fib.append(i)


total = reduce(fibonacci,even)


You could use the sum() function in Python 2.5 but for
your purpose I'd propose using the fib list and using slicing
to select every second element:


L = range(10)
L[::2]

[0, 2, 4, 6, 8]




So you could use

total = sum(fib[::2])

and dispense with evens entirely


Any pointers would be of great help to me.


Frankly I'm puzzled why its using so much RAM.
I'd expect resource usage to be around 20-30MB
tops. hmmm, OK a bit of experimentation shows
that the fibonacci series generates very big numbers
very quickly so each entry is a long number - a very
long number!

21000 characters for the 100,000th entry!

No wonder it blows up.

You have two choices - use floats, which might still
not be big enough! ... It isn't,  98500 out of 10 entries
were infinite using floats! So you need to calculate the
total as you go without saving the values

Or buy a much, much bigger computer! :-)

PS I did all of that investigation using the >>> prompt.
Its a very useful tool for trying things out, I just generated
the list (using 100,000 entries) and examined the contents
using various list comprehensions and len() etc

HTH,

--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld 



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Re: [Tutor] Turtle problem: how to exit the .exe?

[Dick Moores]

At 03:32 PM 7/28/2008, Alan Gauld wrote:


"Dick Moores" <[EMAIL PROTECTED]> wrote

But I'd like to make a version of the script that doesn't report 
any data. How can I write it so that the .exe can be easily exited 
by the user? If Tkinter instead of Turtle were involved, I could 
have an Exit button connected to command=root.quit .


Tkinter is involved, turtle usesw Tkinter.


Yes, I allowed for that when I made the .exe:
python Makespec.py 
-FKc  E:\PyInstaller\MyScripts\randomTriangles_wo_named_colorsV13.exe



But to exit I would expect the standard Windows exit key
combination (Alt F4) to work fine?


Yes, but no. Try it yourself. Please. 



Dick


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Re: [Tutor] Memory error - how to manage large data sets?

[John Fouhy]

On 29/07/2008, Daniel Sarmiento <[EMAIL PROTECTED]> wrote:
>  I tried to run your code and checked (with top) the memory ussage and
>  it uses more than 2 Gb of memory.
>
>  I tried to modify the code a little bit to use less memory and came up
>  with this:
>
>  fib = {0:0,1:1}
>
> even = []
>
>  def fibonacci(x,y):
>return x+y
>
> for j in xrange (2,100):
> i = fib[j-1] + fib[j-2]
> if i % 2 == 0:
> even.append(i)
> fib = {j-1:fib[j-1], j:i}
>
>
>  total = reduce(fibonacci,even)
>  print total
>
>  It looks like the progam still hangs and I did not notice any memory
>  imrovements when running it with 1 000 000

Well, let's see.  You're still storing all the even fibonacci numbers
that you compute.  By the looks of things, one third of fibonacci
numbers are even, so that's about 333,333 numbers that we're storing.

How big do these numbers get?  There's a closed-form expression for
Fibonacci numbers; it's: fib(n) = (phi**n - (1-phi)**n)/sqrt(5), where
phi is the golden ratio (about 1.6).  1-phi is -0.6, so when n is
large, (1-phi)**n is practically zero.  So fib(n) is roughly
phi**n/sqrt(5).  These numbers will quickly get beyond the size of
normal integers, and into long integers.  I don't know how many bytes
a long integer takes up, but I guess we can estimate it by looking at
the log to base 2.

So let's consider the millionth Fibonacci number.  fib(100) ~=
phi**100/sqrt(5).
So log(fib(100)) ~= log(phi**100/sqrt(5)) = 100*log(phi) -
log(sqrt(5)).

Taking logs to base 2, we get:

>>> 100*log(phi, 2) - log(sqrt(5), 2)
694240.75266657001

In other words, the best possible representation of the millionth
Fibonacci number will take almost 700,000 bits, or around 85
kilobytes.  I don't know how Python long integers actually work; it
may take up more space than that.

Of course, that's just the biggest one we're working out.  Let's try
to work out how much space the first million will take up.  This is:

sum_{i=1}^{100} i*log(phi, 2) - log(sqrt(5), 2)

== -100*log(sqrt(5), 2) + log(phi, 2)*sum_{i=1}^{100} i

Remembering the formula for summing integers (n(n+1)/2), this is:

>>> -100*log(sqrt(5), 2) + log(phi, 2)*(100*101/2)
347120142972.21808

This is a number of bits; divide by 8 to get bytes; divide by 8*1024
to get kilobytes, etc:

>>> _/(8*1024*1024*1024)
40.410103156722393

So ... that's about 40 gigabytes worth of numbers in this list you're
trying to build.  Well, actually you're only storing a third of the
Fibonacci numbers (the even ones), so we can cut that down to thirteen
gigabytes.  Assuming my maths is correct and there's not too much
overhead in Python long integers :-)

(the solution, of course, is to avoid storing all those numbers in the
first place)

-- 
John.
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Re: [Tutor] Memory error - how to manage large data sets?

[Chris Fuller]

There's no need to keep any lists.  The sum can be done on the fly, which is 
perhaps a bit slower, but takes a constant amount of ram.  Even storing every 
other element (or every third, which is what he's trying to do: the elements 
that are even numbers, not every other element.. See his example code, or 
Project Euler, problem two, which seems to be the original source) will still 
take a lot of ram.

Something like this:

a = 0
b = 1

total = 0

while True:
   c = a+b
   a = b
   b = c

  if c>1e6:
break

  if c%2 == 0:
total += c

print total

By the way,  working through those problems will really exercise your 
programming and math skills.  It's a great way to get started, if you enjoy 
those kind of puzzles.


Can you see why every third element must be even?
Cheers
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Re: [Tutor] Memory error - how to manage large data sets?

[Alan Gauld]

"Alan Gauld" <[EMAIL PROTECTED]> wrote

> were infinite using floats! So you need to calculate the
> total as you go without saving the values
> 

I got curious so wrote the following function:

>>> def fibtot(N):
...   f0,f1,tot = 0,1,1
...   for n in range(N):
... f = f0 + f1
... f0,f1 = f1,f
... if n % 2 == 0: tot += f
...   return tot

and here are the results...

>>> len(str(fibtot(1)))
2090
>>> len(str(fibtot(10)))
20899
>>> len(str(fibtot(20)))
41798
>>> len(str(fibtot(40)))
83595
>>> len(str(fibtot(50)))
104494
>>> len(str(fibtot(60)))
125393
>>> len(str(fibtot(80)))
167190
>>> len(str(fibtot(100)))
208988
>>>

So the final total contains nearly 209 thousand digits!
Thats a very, very big number... and it took 5 minutes 
to compute on my PC (Dual core 2.8GHz with 2G RAM)

Now I really must go to bed :-)

-- 
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld
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Re: [Tutor] Turtle problem: how to exit the .exe?

[Alan Gauld]

"Dick Moores" <[EMAIL PROTECTED]> wrote


Tkinter is involved, turtle usesw Tkinter.


Yes, I allowed for that when I made the .exe:
python Makespec.py -FKc 
E:\PyInstaller\MyScripts\randomTriangles_wo_named_colorsV13.exe


Means nothing to me, I've never found a need to make an exe
from a python program... :-)


But to exit I would expect the standard Windows exit key
combination (Alt F4) to work fine?


Yes, but no. Try it yourself. Please. 



Very odd, I assume the python script when executed normally
doesn't exhibit such odd behaviour? The only way I could stop
it was to kill the process from Task Manager. Are you sure you
aren't generating some kind of autostart option in your exe
building tool?

I have no further ideas...

Alan G. 



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Re: [Tutor] Turtle problem: how to exit the .exe?

[Dick Moores]

At 05:30 PM 7/28/2008, Alan Gauld wrote:


"Dick Moores" <[EMAIL PROTECTED]> wrote


Tkinter is involved, turtle usesw Tkinter.


Yes, I allowed for that when I made the .exe:
python Makespec.py -FKc 
E:\PyInstaller\MyScripts\randomTriangles_wo_named_colorsV13.exe


Means nothing to me, I've never found a need to make an exe
from a python program... :-)


But to exit I would expect the standard Windows exit key
combination (Alt F4) to work fine?


Yes, but no. Try it yourself. Please. 



Very odd, I assume the python script when executed normally
doesn't exhibit such odd behaviour?


When I try to stop the script from running not by a Ctrl+Q on the 
console window, but on the Turtle window, the only way is to use the 
Task Manager.



The only way I could stop
it was to kill the process from Task Manager.


Yes.


 Are you sure you
aren't generating some kind of autostart option in your exe
building tool?


Well, since the behavior of the .exe is exactly the same as that of 
the running script, I'd say that isn't happening.



I have no further ideas...


Well, thanks for trying, Alan.

Dick


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Re: [Tutor] Memory error - how to manage large data sets?

[Daniel Sarmiento]

>(the solution, of course, is to avoid storing all those numbers in the
>first place)

I tried this:

fib = {0:0,1:1}
sum = 0

for j in xrange (2,100):
i = fib[j-1] + fib[j-2]
if i % 2 == 0:
sum += i
fib = {j-1:fib[j-1], j:i}

print sum

I guess it should come up with the right answer (i compared sum to the
total value for small values in the range and they were the same)

Just storing the value of the sum doesn't use that much memory and
prints the sum for (2, 1 million) but it takes a long time to compute.
I know there has to be a way better solution.
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Re: [Tutor] Tutor Digest, Vol 53, Issue 99

[kinuthiA muchanE]

On Tue, 2008-07-29 at 01:12 +0200, [EMAIL PROTECTED] wrote:
> Message: 3
> Date: Mon, 28 Jul 2008 13:26:13 -0500
> From: "Daniel Sarmiento" <[EMAIL PROTECTED]>
> Subject: Re: [Tutor] Memory error - how to manage large data sets?
> To: tutor@python.org
> Message-ID:
> <[EMAIL PROTECTED]>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Hi
> 
> I tried to run your code and checked (with top) the memory ussage and
> it uses more than 2 Gb of memory.
> 
> I tried to modify the code a little bit to use less memory and came up
> with this:
> 
> fib = {0:0,1:1}
> even = []
> 
> def fibonacci(x,y):
>return x+y
> 
> for j in xrange (2,100):
> i = fib[j-1] + fib[j-2]
> if i % 2 == 0:
> even.append(i)
> fib = {j-1:fib[j-1], j:i}
> 
> total = reduce(fibonacci,even)
> print total
> 
> First, I replaced range with xrange.
> I figured that you only need the last two values in the fibonnaci
> series to calculate the next value, so I replaced the fib list with a
> dictionary to only store the last two values instead of the whole
> series.
> 
> It looks like the progam still hangs and I did not notice any memory
> imrovements when running it with 1 000 000
> 
> Am I wrong thinking that the modifications I made help use less
> memory?
> 
I have realised that when you need to work with large numbers, lists are
slow and tend to gobble up bytes. Another thing try to be as simple as
possible :). This is how I would approach the problem, without using
lists. It produces the result instantly, even for large numbers like a
100, 000, 000.

def fibonacci()
a = 0
b = 1
evenTotal = 0
while a < 1:
a,b = b,a+b
if a%2 == 0:
evenTotal += a
print evenTotal

Does this help?
Kinuthia...

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