Re: arrays in python
On Wed, Sep 23, 2009 at 10:03 PM, AggieDan04 wrote: > On Sep 23, 3:02 pm, Simon Forman wrote: >> On Wed, Sep 23, 2009 at 1:14 PM, Rudolf wrote: >> > Can someone tell me how to allocate single and multidimensional arrays >> > in python. I looked online and it says to do the following x = >> > ['1','2','3','4'] >> >> > However, I want a much larger array like a 100 elements, so I cant >> > possibly do that. I want to allocate an array and then populate it >> > using a for loop. Thanks for your help. >> > -- >> >http://mail.python.org/mailman/listinfo/python-list >> >> In python they're called 'lists'. There are C-style array objects but >> you don't want to use them unless you specifically have to. > ... >> But if you do this: >> >> two_dimensional_list = [ [] for var in some_iterable] >> >> The list of lists you create thereby will contain multiple references >> to the /same/ inner list object. > > No, that creates a list of distinct empty lists. If you want multiple > references to the same inner list, it's > > inner_list = [] > two_dimensional_list = [inner_list for var in some_iterable] > > or > > two_dimensional_list = [[]] * num_copies > -- > http://mail.python.org/mailman/listinfo/python-list > Oh, you're right. I was thinking of the [[]] * n form. My bad. ~Simon -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
On Sep 23, 3:02 pm, Simon Forman wrote: > On Wed, Sep 23, 2009 at 1:14 PM, Rudolf wrote: > > Can someone tell me how to allocate single and multidimensional arrays > > in python. I looked online and it says to do the following x = > > ['1','2','3','4'] > > > However, I want a much larger array like a 100 elements, so I cant > > possibly do that. I want to allocate an array and then populate it > > using a for loop. Thanks for your help. > > -- > >http://mail.python.org/mailman/listinfo/python-list > > In python they're called 'lists'. There are C-style array objects but > you don't want to use them unless you specifically have to. ... > But if you do this: > > two_dimensional_list = [ [] for var in some_iterable] > > The list of lists you create thereby will contain multiple references > to the /same/ inner list object. No, that creates a list of distinct empty lists. If you want multiple references to the same inner list, it's inner_list = [] two_dimensional_list = [inner_list for var in some_iterable] or two_dimensional_list = [[]] * num_copies -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
On Wednesday 23 September 2009 22:12:24 Ethan Furman wrote: > Works great if you want 4,999,999 elements. ;-) Omit the '1' if you > want all five million. Yes. Fenceposts always get me :) And I was just reminded that one can: l=range(500) \d -- home: http://otherwise.relics.co.za/ 2D vector animation : https://savannah.nongnu.org/projects/things/ Font manager : https://savannah.nongnu.org/projects/fontypython/ -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
Donn wrote: On Wednesday 23 September 2009 19:14:20 Rudolf wrote: I want to allocate an array and then populate it using a for loop. You don't need to allocate anything, just use the list or dictionary types. l=[] #empty list for x in range(1,500): l.append(x) \d Works great if you want 4,999,999 elements. ;-) Omit the '1' if you want all five million. ~Ethan~ -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
On Wed, Sep 23, 2009 at 1:22 PM, Donn wrote: > On Wednesday 23 September 2009 19:14:20 Rudolf wrote: >> I want to allocate an array and then populate it >> using a for loop. > You don't need to allocate anything, just use the list or dictionary types. > > l=[] #empty list > for x in range(1,500): > l.append(x) > Of course, in this example you could just say, l = range(1,500) Or in python 3, l = list(range(1,500)) -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
On Wed, Sep 23, 2009 at 1:14 PM, Rudolf wrote: > Can someone tell me how to allocate single and multidimensional arrays > in python. I looked online and it says to do the following x = > ['1','2','3','4'] > > However, I want a much larger array like a 100 elements, so I cant > possibly do that. I want to allocate an array and then populate it > using a for loop. Thanks for your help. > -- > http://mail.python.org/mailman/listinfo/python-list > In python they're called 'lists'. There are C-style array objects but you don't want to use them unless you specifically have to. You can create an empty list like so: x = [] and then put items into it with a for loop like so: for item in some_iterable: x.append(item) But in simple cases like this there's also the "list comprehension" syntax which will do it all in one step: x = [item for item in some_iterable] But again in a case like this, if you're simply populating a list from an iterable source you would just say: x = list(some_iterable) For multidimensional 'arrays' you just put lists in lists. (Or use NumPy if you really want arrays and are doing lots of wild processing on them.) But if you do this: two_dimensional_list = [ [] for var in some_iterable] The list of lists you create thereby will contain multiple references to the /same/ inner list object. This is something that catches many people unawares. You have to go back to using a for loop: x = [] for n in range(100): x.append([(n, m) for m in range(10)]) (That will create a list of one hundred lists, each of which contains ten tuples.) Good luck. -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
Hi! See: http://docs.python.org/tutorial (section 5) @+ -- MCI -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
On Sep 23, 2009, at 1:16 PM, Rudolf wrote: > Can someone tell me how to allocate single and multidimensional arrays > in python. I looked online and it says to do the following x = > ['1','2','3','4'] > > However, I want a much larger array like a 100 elements, so I cant > possibly do that. I want to allocate an array and then populate it > using a for loop. Thanks for your help. Python lists have a dynamic size so you don't usually do that. Instead, we use list comprehensions to stick the for loop inside the list declaration. [str(x) for x in xrange(100)] > > -- > http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
On Wednesday 23 September 2009 19:14:20 Rudolf wrote: > I want to allocate an array and then populate it > using a for loop. You don't need to allocate anything, just use the list or dictionary types. l=[] #empty list for x in range(1,500): l.append(x) \d -- http://mail.python.org/mailman/listinfo/python-list
arrays in python
Can someone tell me how to allocate single and multidimensional arrays in python. I looked online and it says to do the following x = ['1','2','3','4'] However, I want a much larger array like a 100 elements, so I cant possibly do that. I want to allocate an array and then populate it using a for loop. Thanks for your help. -- http://mail.python.org/mailman/listinfo/python-list
Re: Using arrays in Python - problems.
Thanks very much to those who sent me a reply to my array problem! Its now working brilliantly! Best wishes, Gareth. -- [EMAIL PROTECTED] [EMAIL PROTECTED] 665.9238429876 - Number of the Pentium Beast -- http://mail.python.org/mailman/listinfo/python-list
Re: Using arrays in Python - problems.
[EMAIL PROTECTED] wrote: > attackwarningred napisa (a): > > >>The array F(n) is dynamically allocated earlier on and is sized with >>reference to shotcount, the number of iterations the model performs. The >>problem is I can't get something like this to run in Python using numpy, >>and for the size of the array to be sized dynamically with reference to >>the variable shotcount. I acknowledge that my knowledge of Python is >>still really basic (I only started learning it a few days ago) and I'm >>trying to get out of the Fortran programming mindset but I'm stuck and >>don't seem to be able to get any further. If anyone could help I'd be >>really grateful. Thanks very much in advance. > > > Hello. If you want your array to be dynamically resized at every loop > iteration, that might be quite inefficient. How about initialising it > with a required size? > > F = numpy.array([0]*shotcount) > for n in xrange(shotcount): > F[n] = random.lognormvariate(F_mean, F_sd) > > Hope that helps, > Marek > or, F = numpy.random.lognormal(F_mean, F_sd, shotcount) (assuming F_mean, F_sd are the parameters of the distribution, rather than the actual mean and standard deviation). Duncan -- http://mail.python.org/mailman/listinfo/python-list
Re: Using arrays in Python - problems.
[EMAIL PROTECTED] wrote: > attackwarningred napisa (a): > >> The array F(n) is dynamically allocated earlier on and is sized with >> reference to shotcount, the number of iterations the model performs. The >> problem is I can't get something like this to run in Python using numpy, >> and for the size of the array to be sized dynamically with reference to >> the variable shotcount. I acknowledge that my knowledge of Python is >> still really basic (I only started learning it a few days ago) and I'm >> trying to get out of the Fortran programming mindset but I'm stuck and >> don't seem to be able to get any further. If anyone could help I'd be >> really grateful. Thanks very much in advance. > > Hello. If you want your array to be dynamically resized at every loop > iteration, that might be quite inefficient. How about initialising it > with a required size? > > F = numpy.array([0]*shotcount) A more idiomatic version would be this: F = numpy.empty((shotcount,), dtype=float) attackwarningred, you might want to ask your numpy questions on the numpy-discussion mailing list: http://www.scipy.org/Mailing_Lists -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Using arrays in Python - problems.
attackwarningred napisa (a): > The array F(n) is dynamically allocated earlier on and is sized with > reference to shotcount, the number of iterations the model performs. The > problem is I can't get something like this to run in Python using numpy, > and for the size of the array to be sized dynamically with reference to > the variable shotcount. I acknowledge that my knowledge of Python is > still really basic (I only started learning it a few days ago) and I'm > trying to get out of the Fortran programming mindset but I'm stuck and > don't seem to be able to get any further. If anyone could help I'd be > really grateful. Thanks very much in advance. Hello. If you want your array to be dynamically resized at every loop iteration, that might be quite inefficient. How about initialising it with a required size? F = numpy.array([0]*shotcount) for n in xrange(shotcount): F[n] = random.lognormvariate(F_mean, F_sd) Hope that helps, Marek -- http://mail.python.org/mailman/listinfo/python-list
Using arrays in Python - problems.
Dear All, Hello! I've just started to use Python and its a lovely language! I've previously programmed in Fortran 95 and have just began to use numpy. I'm having a few problems with arrays in Python though and wondered if someone could offer me some advice? I wrote the following Fortran code to randomly generate numbers from a log-normal distribution for use in a Monte Carlo model: do n=1,shotcount F(n)=G05DEF(F_mean,F_sd) enddo The array F(n) is dynamically allocated earlier on and is sized with reference to shotcount, the number of iterations the model performs. The problem is I can't get something like this to run in Python using numpy, and for the size of the array to be sized dynamically with reference to the variable shotcount. I acknowledge that my knowledge of Python is still really basic (I only started learning it a few days ago) and I'm trying to get out of the Fortran programming mindset but I'm stuck and don't seem to be able to get any further. If anyone could help I'd be really grateful. Thanks very much in advance. Best wishes, Gareth. -- [EMAIL PROTECTED] 665.9238429876 - Number of the Pentium Beast -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
> Oh, don't tell me, I love playing guessing games! Don't you mean "No no... don't tell me. I'm keen to guess." Sorry, I couldn't resist... :-) (for those who just went huh?, see http://www.aldo.com/sgt/CheeseShoppeSkit.htm) -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
On Fri, 10 Feb 2006 17:50:21 -0500, Kermit Rose wrote: > I want to write a program in python using integer arrays. > > I wish to calculate formulas using 200 digit integers. Must the integers have exactly 200 digits? If you multiply one of these 200-digit integers by ten, should it silently overflow, raise an exception, or become a 201-digit integer? [snip] > The zeros function always gives me an error message. Oh, don't tell me, I love playing guessing games! Is it a SyntaxError? -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
> I want to write a program in python using integer arrays. you can :) > I wish to calculate formulas using 200 digit integers. no problem > I could not find any documentation in python manual about declaring arrays. > > I searched the internet read here http://diveintopython.org/native_data_types/lists.html maybe list are what you are looking for > and found an example that said I must declare > > from Numeric import * yes, one can use Numeric for this taks too > and I downloaded a numerical python extension, > > but still have not found a way to declare an array of given length. > > The zeros function always gives me an error message. >>> import Numeric as N, random as rand >>> nums = [33 ** rand.randint(10,100) for i in range(200)] >>> len(nums) 200 >>> nums[0] 1666465812864030391541732975677083441749008906546726522024522041932256405404932170047036994592860856233379702595619607481259213235163454890913L >>> >>> a = N.array(nums) >>> len(a) 200 >>> a[0] 1666465812864030391541732975677083441749008906546726522024522041932256405404932170047036994592860856233379702595619607481259213235163454890913L >>> by the way, you know you can use interactive Python iterpreter and there is dir and help function >>> dir(a) ['__copy__', '__deepcopy__', 'astype', 'byteswapped', 'copy', 'iscontiguous', 'itemsize', 'resize', 'savespace', 'spacesaver', 'tolist', 'toscalar', 'tostring', 'typecode'] >>> dir(nums) ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__delslice__', '__doc__', '__eq__', '__ge__', '__getattribute__', '__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__setslice__', '__str__', 'append', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort'] >>> Regards, Daniel -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
Kermit Rose wrote:
> From: Kermit Rose
> Date: 02/10/06 17:36:34
> To: [EMAIL PROTECTED]
> Subject: Arrays
>
>
> Hello.
>
> I want to write a program in python using integer arrays.
>
> I wish to calculate formulas using 200 digit integers.
>
> I could not find any documentation in python manual about declaring arrays.
>
> I searched the internet
>
> and found an example that said I must declare
>
> from Numeric import *
>
>
> and I downloaded a numerical python extension,
>
> but still have not found a way to declare an array of given length.
>
> The zeros function always gives me an error message.
>
No need to do anything special. Python allows long integers, and you can
calculate directly with them:
>>> big1 = int('1' + 100*'2')
>>> big2 = int('2' + 100*'3')
>>> big1
1222
2L
>>> big2
2333
3L
>>> big1 + big2
3555
5L
>>>
regards
Steve
--
Steve Holden +44 150 684 7255 +1 800 494 3119
Holden Web LLC www.holdenweb.com
PyCon TX 2006 www.python.org/pycon/
--
http://mail.python.org/mailman/listinfo/python-list
arrays in python
From: Kermit Rose Date: 02/10/06 17:36:34 To: [EMAIL PROTECTED] Subject: Arrays Hello. I want to write a program in python using integer arrays. I wish to calculate formulas using 200 digit integers. I could not find any documentation in python manual about declaring arrays. I searched the internet and found an example that said I must declare from Numeric import * and I downloaded a numerical python extension, but still have not found a way to declare an array of given length. The zeros function always gives me an error message. Kermit <[EMAIL PROTECTED] > -- http://mail.python.org/mailman/listinfo/python-list
Re: Long integer arrays in Python; how? /Carl
Carl wrote: > I have the following problem > > import Numeric > dim = 1 > bits = 32 > v = Numeric.zeros((dim, bits), 'l') > for j in range(bits): > v[0][j] = 1L << bits - j - 1 > > The problem is the last assignment, which is not valid, since the integer is > on the right hand side is to large to be assigned to an array element. Use Numeric.UnsignedInt32 as the data type. -- Robert Kern [EMAIL PROTECTED] "In the fields of hell where the grass grows high Are the graves of dreams allowed to die." -- Richard Harter -- http://mail.python.org/mailman/listinfo/python-list
Long integer arrays in Python; how? /Carl
I have the following problem import Numeric dim = 1 bits = 32 v = Numeric.zeros((dim, bits), 'l') for j in range(bits): v[0][j] = 1L << bits - j - 1 The problem is the last assignment, which is not valid, since the integer is on the right hand side is to large to be assigned to an array element. Is there a way around this problem in Python? Yours /Carl -- http://mail.python.org/mailman/listinfo/python-list
