Quoting from a numpy discussion list:

&gt; That information is available via `numpy.finfo()` and `numpy.iinfo()`:
&gt;     
&gt;     In [12]: finfo(&#39;d&#39;).max
&gt;     Out[12]: 1.7976931348623157e+308
&gt;     
&gt;     In [13]: iinfo(&#39;i&#39;).max
&gt;     Out[13]: 2147483647
&gt;     
&gt;     In [14]: iinfo(&#39;uint8&#39;).max
&gt;     Out[14]: 255

Link [here][1].


  [1]: http://www.mail-archive.com/numpy-discussion@scipy.org/msg09903.html

You can use [`numpy.iinfo(arg).max`][1] to find the max value for integer types of `arg`, and [`numpy.finfo(arg).max`][2] to find the max value for float types of `arg`.

    &gt;&gt;&gt; numpy.iinfo(numpy.uint64).min
    0
    &gt;&gt;&gt; numpy.iinfo(numpy.uint64).max
    18446744073709551615L
    &gt;&gt;&gt; numpy.finfo(numpy.float64).max
    1.7976931348623157e+308
    &gt;&gt;&gt; numpy.finfo(numpy.float64).min
    -1.7976931348623157e+308

`iinfo` only offers `min` and `max`, but `finfo` also offers useful values such as `eps` (the smallest number &gt; 0 representable) and `resolution` (the approximate decimal number resolution of the type of `arg`).


  [1]: http://docs.scipy.org/doc/numpy/reference/generated/numpy.iinfo.html
  [2]: http://docs.scipy.org/doc/numpy/reference/generated/numpy.finfo.html

Running a Ruby on Rails (RoR) app or Ruby code which uses the ActiveRecord framework, you get the error message:

&gt; Please install the postgresql adapter:
&gt; `gem install
&gt; activerecord-postgresql-adapter`

Trying to run:

    gem install activerecord-postgresql-adapter

also fails, leaving you at a loss.


How to handle Ruby on Rails error: &quot;Please install the postgresql adapter: `gem install activerecord-postgresql-adapter&#39;&quot;

has anyone successfully mapped a numeric array in PostgreSQL to a numeric array in java via Hibernate?

sql:

    CREATE TABLE sal_emp (name text, pay_by_quarter integer[]);
    INSERT INTO sal_emp VALUES (&#39;one&#39;, &#39;{1,2,3}&#39;);
    INSERT INTO sal_emp VALUES (&#39;two&#39;, &#39;{4,5,6}&#39;);
    INSERT INTO sal_emp VALUES (&#39;three&#39;, &#39;{2,4,6}&#39;);

&lt;?xml version=&quot;1.0&quot;?&gt;
&lt;!DOCTYPE hibernate-mapping PUBLIC &quot;-//Hibernate/Hibernate Mapping DTD 3.0//EN&quot; &quot;http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd&quot;&gt;

mapping:

    &lt;hibernate-mapping&gt;
    	&lt;class name=&quot;SalEmp&quot; table=&quot;sal_emp&quot;&gt;
    		&lt;id name=&quot;name&quot; /&gt;
    		&lt;property name=&quot;payByQuarter&quot; column=&quot;pay_by_quarter&quot; /&gt;
    	&lt;/class&gt;
    &lt;/hibernate-mapping&gt;

class:

    public class SalEmp implements Serializable{
        private String name;
        private Integer[] payByQuarter;
        ...// getters &amp; setters
    }

i get an exception when querying the table.

How to map a PostgreSQL array with Hibernate

I&#39;m interested in finding for a particular Numpy type (e.g. `np.int64`, `np.uint32`, `np.float32`, etc.) what the range of all possible valid values is (e.g. `np.int32` can store numbers up to `2**31-1`). Of course, I guess one can theoretically figure this out for each type, but is there a way to do this at run time to ensure more portable code?

How to get the range of valid Numpy data types?

<p>I'm interested in finding for a particular Numpy type (e.g. <code>np.int64</code>, <code>np.uint32</code>, <code>np.float32</code>, etc.) what the range of all possible valid values is (e.g. <code>np.int32</code> can store numbers up to <code>2**31-1</code>). Of course, I guess one can theoretically figure this out for each type, but is there a way to do this at run time to ensure more portable code?</p>


[File-like objects][1] are objects in Python that behave like a real file, e.g. have a read() and a write method(), but have a different implementation from `file`. It is realization of the [Duck Typing][2] concept.

It is considered a good practice to allow a file-like object everywhere where a file is expected so that e.g. a [StringIO][3] or a Socket object can be used instead a real file. So it is bad to perform a check like this:


    if not isinstance(fp, file):
       raise something

What is the best way to check if an object (e.g. a parameter of a method) is &quot;file-like&quot;?


  [1]: http://docs.python.org/library/stdtypes.html#bltin-file-objects
  [2]: http://en.wikipedia.org/wiki/Duck_typing
  [3]: http://docs.python.org/library/stringio.html

Check if object is file-like in Python

I am using the Boto library to talk to AWS. I want to disable logging. (Or redirect to /dev/null or other file). I can&#39;t find an obvious way to do this. I tried this, but that doesn&#39;t seem to help:

    import boto
    boto.set_file_logger(&#39;boto&#39;, &#39;logs/boto.log&#39;)


This says it is possible, http://developer.amazonwebservices.com/connect/thread.jspa?messageID=52727&amp;#52727 but as far as I know the documentation doesn&#39;t tell how.

Disable boto logging without modifying the boto files

Is there a

    do until x:
        ...

in Python, or a nice way to implement such a looping construct?


Is there a &quot;do ... until&quot; in Python?

I&#39;m using urllib2 to fetch a a page via HTTP.  Sometimes the resource throws a HTTP error 400 (Bad Request) when my request contains an error.  However, that response also contains an XML element that gives a detailed error message.  It would be very handy to be able to see that error rather than just the HTTPError exception returned by urllib2.  

How do I return the document contents in spite of the exception?

Python urllib2: Reading content body even during HTTPError exception?

I have two iterables in Python, and I want to go over them in pairs:

    foo = (1, 2, 3)
    bar = (4, 5, 6)
    
    for (f, b) in some_iterator(foo, bar):
        print(&quot;f: &quot;, f, &quot;; b: &quot;, b)

It should result in:

    f: 1; b: 4
    f: 2; b: 5
    f: 3; b: 6

*One* way to do it is to iterate over the indices:

    for i in range(len(foo)):
        print(&quot;f: &quot;, foo[i], &quot;; b: &quot;, bar[i])

But that seems somewhat unpythonic to me. Is there a better way to do it?


How to iterate through two lists in parallel?

I have the following code:

    r = numpy.zeros(shape = (width, height, 9))

It creates a `width x height x 9` matrix filled with zeros. Instead, I&#39;d like to know if there&#39;s a function or way to initialize them instead to `NaN`s in an easy way.

Create numpy matrix filled with NaNs

I would like to execute the equivalent of the following MATLAB code using NumPy: `repmat([1; 1], [1 1 1])`.  How would I accomplish this?

What is the equivalent of MATLAB&#39;s repmat in NumPy

I&#39;d like to use principal component analysis (PCA) for dimensionality reduction.  Does numpy or scipy already have it, or do I have to roll my own using [`numpy.linalg.eigh`][1]?

I don&#39;t just want to use singular value decomposition (SVD) because my input data are quite high-dimensional (~460 dimensions), so I think SVD will be slower than computing the eigenvectors of the covariance matrix.

I was hoping to find a premade, debugged implementation that already makes the right decisions for when to use which method, and which maybe does other optimizations that I don&#39;t know about.


  [1]: http://docs.scipy.org/doc/numpy/reference/generated/numpy.linalg.eigh.html

Principal component analysis in Python

After doing some processing on an audio or image array, it needs to be normalized within a range before it can be written back to a file.  This can be done like so:

    # Normalize audio channels to between -1.0 and +1.0
    audio[:,0] = audio[:,0]/abs(audio[:,0]).max()
    audio[:,1] = audio[:,1]/abs(audio[:,1]).max()
    
    # Normalize image to between 0 and 255
    image = image/(image.max()/255.0)

Is there a less verbose, convenience function way to do this? `matplotlib.colors.Normalize()` doesn&#39;t seem to be related.


How to normalize a NumPy array to within a certain range?

Numpy&#39;s meshgrid is very useful for converting two vectors to a coordinate grid. What is the easiest way to extend this to three dimensions? So given three vectors x, y, and z, construct 3x3D arrays (instead of 2x2D arrays) which can be used as coordinates.

Numpy meshgrid in 3D

Let&#39;s say I have a **LazySeq** of *java.lang.Character* like

    (\b \ \! \/ \b \ \% \1 \9 \/ \. \i \% \$ \i \space \^@)

How can I convert this to a String? I&#39;ve tried the obvious

    (String. my-char-seq)

but it throws

    java.lang.IllegalArgumentException: No matching ctor found for class java.lang.String (NO_SOURCE_FILE:0)
    [Thrown class clojure.lang.Compiler$CompilerException]

I think because the String constructor expects a primitive **char[]** instead of a **LazySeq**. So then I tried something like

    (String. (into-array my-char-seq))

but it throws the same exception. The problem now is that **into-array** is returning a **java.lang.Character[]** instead of a primitive **char[]**. This is frustrating, because I actually generate my character sequence like this

    (map #(char (Integer. %)) seq-of-ascii-ints)

Basically I have a seq of ints representing ASCII characters; 65 = A, etc. You can see I explicitly use the primitive type coercion function **(char x)**.

What this means is that my **map** function is returning a primitive **char** but the Clojure **map** function overall is returning the *java.lang.Character* object.
 






How can I convert a LazySeq of Characters to a String in Clojure?

In Python, when should you use lists and when tuples?

Sometimes you don&#39;t have a choice, for example if you have

    &quot;hello %s you are %s years old&quot; % x

then x must be a tuple.

But if I am the one who designs the API and gets to choose the data types, then what are the guidelines?

List vs tuple, when to use each?

Is there a way to determine whether or not a given .Net Type is a number? For example: `System.UInt32/UInt16/Double` are all numbers. I want to avoid a long switch-case on the `Type.FullName`.

C# - how to determine whether a Type is a number

How to check programmatically if a type is a struct or a class?

This is what I normally do in order to ascertain that the input is a `list`/`tuple` - but not a `str`. Because many times I stumbled upon bugs where a function passes a `str` object by mistake, and the target function does `for x in lst` assuming that `lst` is actually a `list` or `tuple`.

    assert isinstance(lst, (list, tuple))

My question is: is there a better way of achieving this?


Content Type	Original Author	Original Content on Stackoverflow
Question	astrofrog	View Question on Stackoverflow
Solution 1 - Python	perimosocordiae	View Answer on Stackoverflow
Solution 2 - Python	Mark Rushakoff	View Answer on Stackoverflow

How to get the range of valid Numpy data types?

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

How to map a PostgreSQL array with Hibernate

How to handle Ruby on Rails error: "Please install the postgresql adapter: `gem install activerecord-postgresql-adapter'"

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