Re: [Tutor] From Numpy Import *
> Thank-you! It is important for us to avoid potential code > conflicts and so we'll standardize on the import > syntax. > > On a related note: > We are using both NumPy and SciPy. Consider the example y = Ax > where A is a sparse matrix. If A is qualified as a scipy object > then do y and x also have to be scipy objects or can they be numpy > objects? scipy is mostly written with numpy as its core, so in general you should be able to use numpy objects with scipy objects (not sure, but I guess most scipy objects will have a numpy object as their base). The best is simply to try it out! In this particular case, x can be a numpy array; y is created in the process, so will be the type of object most suited to the outcome of the equation (ie, you cannot state beforehand if it's a numpy or scipy object); in this case, again a numpy array. See also the scipy tutorial on the scipy.org website, where numpy and scipy objects are freely mixed. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] From Numpy Import *
Thank-you! It is important for us to avoid potential code conflicts and so we'll standardize on the import syntax. On a related note: We are using both NumPy and SciPy. Consider the example y = Ax where A is a sparse matrix. If A is qualified as a scipy object then do y and x also have to be scipy objects or can they be numpy objects? Dinesh - Original Message - From: Michael H. Goldwasser To: Dinesh B Vadhia Cc: tutor@python.org Sent: Wednesday, November 07, 2007 5:37 PM Subject: [Tutor] From Numpy Import * On Wednesday November 7, 2007, Dinesh B Vadhia wrote: >Hello! The standard Python practice for importing modules is, for example: > >import sys >import os >etc. > >In NumPy (and SciPy) the 'book' suggests using: > >from numpy import * >from scipy import * > >However, when I instead use 'import numpy' it causes all sorts of errors > in my existing code. The issue is the following. The numpy module includes many definitions, for example a class named array. When you use the syntax, from numpy import * That takes all definitions from the module and places them into your current namespace. At this point, it would be fine to use a command such as values = array([1.0, 2.0, 3.0]) which instantiates a (numpy) array. If you instead use the syntax import numpy things brings that module as a whole into your namespace, but to access definitions from that module you have to give a qualified name, for example as values = numpy.array([1.0, 2.0, 3.0]) You cannot simply use the word array as in the first scenario. This would explain why your existing code would no longer work with the change. >What do you suggest? The advantage of the "from numpy import *" syntax is mostly convenience. However, the better style is "import numpy" precisely becuase it does not automatically introduce many other definitions into your current namespace. If you were using some other package that also defined an "array" and then you were to use the "from numpy import *", the new definition would override the other definition. The use of qualified names helps to avoid these collisions and makes clear where those definitions are coming from. With regard, Michael ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] From Numpy Import *
Michael H. Goldwasser wrote: >from numpy import * >import numpy There is a third option which provides the safety/control of import numpy with a little less typing: import numpy as np values = np.array([1.0, 2.0, 3.0]) and you can also import just the names you need: from numpy import array values = array(...) Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] From Numpy Import *
On Wednesday November 7, 2007, Dinesh B Vadhia wrote: >Hello! The standard Python practice for importing modules is, for example: > >import sys >import os >etc. > >In NumPy (and SciPy) the 'book' suggests using: > >from numpy import * >from scipy import * > >However, when I instead use 'import numpy' it causes all sorts of errors > in my existing code. The issue is the following. The numpy module includes many definitions, for example a class named array. When you use the syntax, from numpy import * That takes all definitions from the module and places them into your current namespace. At this point, it would be fine to use a command such as values = array([1.0, 2.0, 3.0]) which instantiates a (numpy) array. If you instead use the syntax import numpy things brings that module as a whole into your namespace, but to access definitions from that module you have to give a qualified name, for example as values = numpy.array([1.0, 2.0, 3.0]) You cannot simply use the word array as in the first scenario. This would explain why your existing code would no longer work with the change. >What do you suggest? The advantage of the "from numpy import *" syntax is mostly convenience. However, the better style is "import numpy" precisely becuase it does not automatically introduce many other definitions into your current namespace. If you were using some other package that also defined an "array" and then you were to use the "from numpy import *", the new definition would override the other definition. The use of qualified names helps to avoid these collisions and makes clear where those definitions are coming from. With regard, Michael ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] From Numpy Import *
Hello! The standard Python practice for importing modules is, for example: import sys import os etc. In NumPy (and SciPy) the 'book' suggests using: from numpy import * from scipy import * However, when I instead use 'import numpy' it causes all sorts of errors in my existing code. What do you suggest? Dinesh ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
