How do you do arrays

[Thomas Bunce]

I am new at Pyton and I am learning from book not classes
so please forgive my being slow

The below does not work I get an Error of File
"Matrix[index] = k
NameError: name 'iMatrix' is not defined"

while index < majorlop1:
index = index + 1
k = random.choice(l istvalues) + 1
iMatrix[index] = k

The book statement of
array(typecode, initializer) does not make sence
to me how it henerates ore relaes to the org name
for the array.

Thank You
Tom

[Kartic]

Re: How do you do arrays

Tom,

Before you use iMatrix[index], you have to tell python to use iMatrix
as an array. You will do that using iMatrix = [] *outside* the loop.

iMatrix = []
while index < majorlop1: # rest of the loop statements

Since you are new, please take a look at the Python tutorial to get you
started.

http://docs.python.org/tut/tut.html

Thanks,
-Kartic

[Kartic]

Re: How do you do arrays

and it is called a "List" in Python parlance.

[Sean Blakey]

Re: How do you do arrays

On Tue, 01 Feb 2005 10:52:45 -0800, Thomas Bunce <tbunce@mac.com > wrote:[color=blue]
> I am new at Pyton and I am learning from book not classes
> so please forgive my being slow
>
> The below does not work I get an Error of File
> "Matrix[index] = k
> NameError: name 'iMatrix' is not defined"
>
> while index < majorlop1:
> index = index + 1
> k = random.choice(l istvalues) + 1
> iMatrix[index] = k
>
> The book statement of
> array(typecode, initializer) does not make sence
> to me how it henerates ore relaes to the org name
> for the array.
>
> Thank You
> Tom
> --
> http://mail.python.org/mailman/listinfo/python-list
>[/color]
Like any other variable, you need to declare iMatrix before you use it:
$ python
Python 2.4 (#1, Dec 28 2004, 12:08:51)
[GCC 3.3 20030304 (Apple Computer, Inc. build 1495)] on darwin
Type "help", "copyright" , "credits" or "license" for more information.[color=blue][color=green][color=darkred]
>>> import random
>>> import array
>>> index = 0
>>> majorlop1 = 4
>>> iMatrix = array.array('b' )
>>> listvalues = [1, 2, 3, 4]
>>> while index < majorlop1:[/color][/color][/color]
.... index = index + 1
.... k = random.choice(l istvalues) + 1
.... iMatrix.append( k)
....[color=blue][color=green][color=darkred]
>>> iMatrix[/color][/color][/color]
array('b', [3, 5])[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

You should probably look at the wealth of information at
http://www.python.org/doc - the tutorial is a good start on how to use
the language, and the library reference has much more depth on the
array module.

http://docs.python.org/lib/module-array.html

--
Sean Blakey
Saint of Mild Amusement, Evil Genius, Big Geek
Python/Java/C++/C(Unix/Windows/Palm/Web) developer
quine = ['print "quine =",quine,"; exec(quine[0])"'] ; exec(quine[0])

[wes weston]

Re: How do you do arrays

Thomas Bunce wrote:[color=blue]
> I am new at Pyton and I am learning from book not classes
> so please forgive my being slow
>
> The below does not work I get an Error of File
> "Matrix[index] = k
> NameError: name 'iMatrix' is not defined"
>
> while index < majorlop1:
> index = index + 1
> k = random.choice(l istvalues) + 1
> iMatrix[index] = k
>
> The book statement of
> array(typecode, initializer) does not make sence
> to me how it henerates ore relaes to the org name
> for the array.
>
> Thank You
> Tom[/color]

Thomas,
You can do
[color=blue][color=green][color=darkred]
>>> m = [4]
>>> m[/color][/color][/color]
[4]

wes

[Kartic]

Re: How do you do arrays

Tom,

It has to be iMatrix.append( k), not iMatrix[index] = k. Python will
give an error - list assignment index out of range - for that.
Just curious - what book are you following?

-Kartic

[Thomas Bunce]

Re: How do you do arrays

Thanks all

Tom

[beliavsky@aol.com]

Re: How do you do arrays

If you want do numerical calculations with vectors and matrices, you
should probably use the Numarray module. Python's built-in lists are
not intended for heavy numerical computations. They are more flexible
than the arrays in languages like C and Fortran in that they can store
elements of different types. One can write, for example,
x = ["dog",1,2.3] .

[Thomas Bunce]

Re: How do you do arrays

Tryed it and this is what I got (I did go to the web sight)

tom(h=500)$ /tmp/501/Cleanup\ At\ Startup/ptesting-128981347.87.py .command; exit
Input the maximu number of tvalue: 114
Traceback (most recent call last):
File "/Users/tom/Desktop/ptesting.py", line 20, in ?
iMatrix[index] = k
IndexError: list assignment index out of range
logout
[Process completed]

The complete listing:

#!/usr/bin/python
import random
import sys
import array
#
### generates a list of numbers between 1 and target
### and uses 23 % of these values.
#

iMatrix = []

tvalue = input('Input the maximu number of tvalue: ')
majorlop1 = int tvalue * .23)
listvalues = range(tvalue)

sep = '- '
index = 0
while index < majorlop1:
index = index + 1
k = random.choice(l istvalues) + 1
iMatrix[index] = k

while index < majorlop1:
print '- %s %s' % (iMatrix[index], sep)
#
###
#
I would like to set the size of the List/array independent
of having to intialialize it prior to use.
If it help I will say the bad works I am using OSX

Thanks Tom
In article <1107284817.848 551.79000@c13g2 000cwb.googlegr oups.com>,
"Kartic" <kartic.krishna murthy@gmail.co m> wrote:
[color=blue]
> Tom,
>
> Before you use iMatrix[index], you have to tell python to use iMatrix
> as an array. You will do that using iMatrix = [] *outside* the loop.
>
> iMatrix = []
> while index < majorlop1: # rest of the loop statements
>
> Since you are new, please take a look at the Python tutorial to get you
> started.
> http://docs.python.org/tut/tut.html
>
> Thanks,
> -Kartic[/color]

[wes weston]

Re: How do you do arrays

Thomas,
If you were allowed to do what you're doing, the
list first element would be getting skipped as "index"
is always > 0. The thing is, you don't want the "index"
var at all for adding to the list; just do jMatrix.append( k).
You can iterate over the list with
for x in jMatrix:
print x

Is it basic that indexes from 1 vs. 0? 'just about
completely forgotten basic.
wes

Thomas Bunce wrote:[color=blue]
> Tryed it and this is what I got (I did go to the web sight)
>
> tom(h=500)$ /tmp/501/Cleanup\ At\ Startup/ptesting-128981347.87.py .command; exit
> Input the maximu number of tvalue: 114
> Traceback (most recent call last):
> File "/Users/tom/Desktop/ptesting.py", line 20, in ?
> iMatrix[index] = k
> IndexError: list assignment index out of range
> logout
> [Process completed]
>
> The complete listing:
>
> #!/usr/bin/python
> import random
> import sys
> import array
> #
> ### generates a list of numbers between 1 and target
> ### and uses 23 % of these values.
> #
>
> iMatrix = []
>
> tvalue = input('Input the maximu number of tvalue: ')
> majorlop1 = int tvalue * .23)
> listvalues = range(tvalue)
>
> sep = '- '
> index = 0
> while index < majorlop1:
> index = index + 1
> k = random.choice(l istvalues) + 1
> iMatrix[index] = k
>
> while index < majorlop1:
> print '- %s %s' % (iMatrix[index], sep)
> #
> ###
> #
> I would like to set the size of the List/array independent
> of having to intialialize it prior to use.
> If it help I will say the bad works I am using OSX
>
> Thanks Tom
> In article <1107284817.848 551.79000@c13g2 000cwb.googlegr oups.com>,
> "Kartic" <kartic.krishna murthy@gmail.co m> wrote:
>
>[color=green]
>>Tom,
>>
>>Before you use iMatrix[index], you have to tell python to use iMatrix
>>as an array. You will do that using iMatrix = [] *outside* the loop.
>>
>>iMatrix = []
>>while index < majorlop1: # rest of the loop statements
>>
>>Since you are new, please take a look at the Python tutorial to get you
>>started.
>>http://docs.python.org/tut/tut.html
>>
>>Thanks,
>>-Kartic[/color][/color]

[beliavsky@aol.com]

Re: How do you do arrays

wes weston wrote:[color=blue]
> Thomas,
> If you were allowed to do what you're doing, the
> list first element would be getting skipped as "index"
> is always > 0. The thing is, you don't want the "index"
> var at all for adding to the list; just do jMatrix.append( k).
> You can iterate over the list with
> for x in jMatrix:
> print x
>
> Is it basic that indexes from 1 vs. 0? 'just about
> completely forgotten basic.
> wes[/color]

I think most versions of Basic have arrays that by default start with
1, as did their ancestor, Fortran, although other lower bounds can be
specified. VB.NET, Microsoft's successor to Visual Basic, requires
arrays to start with zero.

[Kartic]

Re: How do you do arrays

Tom - I answered your question even before you posted it!

You have to use iMatrix.append( k) and NOT iMatrix[index] = k.

Also, what do you expect out of:
while index < majorlop1:
print '- %s %s' % ( iMatrix[index], sep)

This loop will never get executed because your previous loop finishes
due to the same condition index < majorlop1.

I am not sure what book you are using but I don't think it is a very
good one.
[color=blue]
> I would like to set the size of the List/array independent
> of having to intialialize it prior to use.[/color]

You can do the following when you allocate your list.
iMatrix = [''] * size # where size is an integer
and this will give you a list of size empty elements. If you do this,
do not use iMatrix.append( ). Use the array notation like you have in
you code currently.

Thanks
-Kartic

[Thomas Bunce]

Re: How do you do arrays

Learning Python O'Reilly book and Python In A Nut Shell and about 2 inchs
printed of Web information

Tom

In article <1107286861.714 451.288010@f14g 2000cwb.googleg roups.com>,
"Kartic" <kartic.krishna murthy@gmail.co m> wrote:
[color=blue]
> Tom,
>
> It has to be iMatrix.append( k), not iMatrix[index] = k. Python will
> give an error - list assignment index out of range - for that.
> Just curious - what book are you following?
>
> -Kartic[/color]

[Thomas Bunce]

Re: How do you do arrays


It was when I saw a use of complex numbers as a usable statement I became
interested in Python

Tom


In article <1107288521.396 952.154000@z14g 2000cwz.googleg roups.com>,
beliavsky@aol.c om wrote:
[color=blue]
> If you want do numerical calculations with vectors and matrices, you
> should probably use the Numarray module. Python's built-in lists are
> not intended for heavy numerical computations. They are more flexible
> than the arrays in languages like C and Fortran in that they can store
> elements of different types. One can write, for example,
> x = ["dog",1,2.3] .[/color]

[Dan Perl]

Re: How do you do arrays

A solution that I haven't seen mentioned by other postings in the thread is
to implement the array as a dictionary:

iMatrix = {}
for index in range(majorlop1 ):
k = random.choice(l istvalues) + 1
iMatrix[index] = k

Mind you, a dictionary does not behave *exactly* like an array. For
instance, in your example, you may later do a "del iMatrix[2]" and then you
wouldn't really be able to use iMatrix like an array anymore. But,
depending on your application, a dictionary may be perfectly suitable.

Hope this helps.

Dan

"Thomas Bunce" <tbunce@mac.com > wrote in message
news:tbunce-010205105245000 1@192.168.1.12. ..[color=blue]
>I am new at Pyton and I am learning from book not classes
> so please forgive my being slow
>
> The below does not work I get an Error of File
> "Matrix[index] = k
> NameError: name 'iMatrix' is not defined"
>
> while index < majorlop1:
> index = index + 1
> k = random.choice(l istvalues) + 1
> iMatrix[index] = k
>
> The book statement of
> array(typecode, initializer) does not make sence
> to me how it henerates ore relaes to the org name
> for the array.
>
> Thank You
> Tom[/color]