Re: numpy arrays to python compatible arrays
On Jun 11, 12:29 am, Martin mdeka...@gmail.com wrote: On Jun 10, 9:02 pm, Philip Semanchuk phi...@semanchuk.com wrote: On Jun 10, 2010, at 9:58 AM,JavierMontoyawrote: Dear all, I'm new to python and have been working with the numpy package. I have some numpy float arrays (obtained from np.fromfile and np.cov functions) and would like to convert them to simple python arrays. I was wondering which is the best way to do that? Is there any function to do that? HiJavier, Since you are new to Python I'll ask whether you want to convert Numpy arrays to Python arrays (as you stated) or Python lists. Python lists are used very frequently; Python arrays see very little use outside of numpy. If you can use a Python list, the .tolist() member of the numpy array object should do the trick. bye P as Philip said...though I very much doubt you really want to do this? Why wouldn't you just keep it in a numpy array? Thanks for the suggestions! The main reason not to use a numpy array is because I'm using a package that doesn't work with numpy arrays. With the .tolist() conversion it's now working fine, thanks! -- http://mail.python.org/mailman/listinfo/python-list
numpy arrays to python compatible arrays
Dear all, I'm new to python and have been working with the numpy package. I have some numpy float arrays (obtained from np.fromfile and np.cov functions) and would like to convert them to simple python arrays. I was wondering which is the best way to do that? Is there any function to do that? Best wishes -- http://mail.python.org/mailman/listinfo/python-list
Re: numpy arrays to python compatible arrays
On Jun 10, 2010, at 9:58 AM, Javier Montoya wrote: Dear all, I'm new to python and have been working with the numpy package. I have some numpy float arrays (obtained from np.fromfile and np.cov functions) and would like to convert them to simple python arrays. I was wondering which is the best way to do that? Is there any function to do that? Hi Javier, Since you are new to Python I'll ask whether you want to convert Numpy arrays to Python arrays (as you stated) or Python lists. Python lists are used very frequently; Python arrays see very little use outside of numpy. If you can use a Python list, the .tolist() member of the numpy array object should do the trick. bye P -- http://mail.python.org/mailman/listinfo/python-list
Re: numpy arrays to python compatible arrays
On Jun 10, 9:02 pm, Philip Semanchuk phi...@semanchuk.com wrote: On Jun 10, 2010, at 9:58 AM, Javier Montoya wrote: Dear all, I'm new to python and have been working with the numpy package. I have some numpy float arrays (obtained from np.fromfile and np.cov functions) and would like to convert them to simple python arrays. I was wondering which is the best way to do that? Is there any function to do that? Hi Javier, Since you are new to Python I'll ask whether you want to convert Numpy arrays to Python arrays (as you stated) or Python lists. Python lists are used very frequently; Python arrays see very little use outside of numpy. If you can use a Python list, the .tolist() member of the numpy array object should do the trick. bye P as Philip said...though I very much doubt you really want to do this? Why wouldn't you just keep it in a numpy array? -- 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: 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
Re: arrays in python
On Sep 23, 2009, at 1:16 PM, Rudolf yellowblueyel...@gmail.com 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
Hi! See: http://docs.python.org/tutorial (section 5) @+ -- MCI -- http://mail.python.org/mailman/listinfo/python-list
Re: arrays in python
On Wed, Sep 23, 2009 at 1:14 PM, Rudolf yellowblueyel...@gmail.com 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
On Wed, Sep 23, 2009 at 1:22 PM, Donn donn.in...@gmail.com 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
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 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
On Sep 23, 3:02 pm, Simon Forman sajmik...@gmail.com wrote: On Wed, Sep 23, 2009 at 1:14 PM, Rudolf yellowblueyel...@gmail.com 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 Wed, Sep 23, 2009 at 10:03 PM, AggieDan04 danb...@yahoo.com wrote: On Sep 23, 3:02 pm, Simon Forman sajmik...@gmail.com wrote: On Wed, Sep 23, 2009 at 1:14 PM, Rudolf yellowblueyel...@gmail.com 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
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: 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
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.
[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.
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
rpy: parsing arrays from python to R
Hi,
I use rpy on linux to call R functions. Works fine up to the following
problem: How to parse arrays (no vectors, that means 2-dimensional) to
R without much effort?
The following code solves the problem (in two different ways).
However, it seems to me that there might be a way to do it more
efficiently.
rpy.r.assign(N, N)
rpy.r(A2 - array(1:N^2, dim=c(N,N)))
rpy.r(A3 - array(1:N^2, dim=c(N,N)))
for i in range(N): # two alternative ways to parse
arrays
rpy.r.assign(Wi, W[i])
rpy.r.assign(i, i+1)
rpy.r(for( j in 1:N ){
A2[i,j] - Wi[j]})
for k in range(N):
rpy.r.assign(k, k+1)
rpy.r(A3[i,k] - Wi[k])
print rpy.r(A3)
print rpy.r(A2)
As I see it, the problem is, that the 'assign' command works only
either for scalars or vectors (one-dimensional arrays but not more-
dimensional arrays). I tried it for 2-dimensional arrays and the
result is a list whose components are vectors. Again, this is easy to
convert to a two-dimensional array but the point here is that one has
to do it.
Maybe there are people using R with python who have some more
experience. I would be interested how they solved this problem.
Thanks!
Frank
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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: 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
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Holden Web LLC www.holdenweb.com
PyCon TX 2006 www.python.org/pycon/
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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
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
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
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
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
