boost/python
2
0
Fork 0
mirror of https://github.com/boostorg/python.git synced 2026-01-23 05:42:30 +00:00
Code Issues Projects Releases Wiki Activity

Deploy to GitHub Pages: 080eb55be6

Browse Source
This commit is contained in:
Travis CI
2016-10-10 17:21:42 +00:00
parent 34e61298c9
commit f6474f3914
40 changed files with 1029 additions and 324 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
develop/doc/html/numpy/tutorial/ndarray.html
View File

@@ -7,8 +7,8 @@
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Creating ndarrays - Boost.Python NumPy extension 1.0 documentation</title>
<link rel="stylesheet" href="../_static/style.css" type="text/css" />
<link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
<link rel="stylesheet" href="../_static/style.css" type="text/css" />
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT: '../',
@@ -37,8 +37,8 @@
alt="C++ Boost" src="../_static/bpl.png" border="0"></a></h3>
</td>
<td valign="top">
<!-- <h1 align="center"><a href="../index.html">Boost.NumPy</a></h1>-->
<td >
<h1 align="center"><a href="../index.html">(NumPy)</a></h1>
<!-- <h2 align="center">CallPolicies Concept</h2>-->
</td>
<td>
@@ -85,14 +85,14 @@ ndarrays can also be created from arbitrary python sequences as well as from dat
</pre></div>
</div>
<p>Let&#8217;s now create an ndarray from a simple tuple. We first create a tuple object, and then pass it to the array method, to generate the necessary tuple</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">object</span> <span class="n">tu</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="sc">&#39;a&#39;</span><span class="p">,</span><span class="sc">&#39;b&#39;</span><span class="p">,</span><span class="sc">&#39;c&#39;</span><span class="p">)</span> <span class="p">;</span>
<span class="n">np</span><span class="o">::</span><span class="n">ndarray</span> <span class="n">example_tuple</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">array</span><span class="p">(</span><span class="n">tu</span><span class="p">)</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">object</span> <span class="n">tu</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="sc">&#39;a&#39;</span><span class="p">,</span><span class="sc">&#39;b&#39;</span><span class="p">,</span><span class="sc">&#39;c&#39;</span><span class="p">);</span>
<span class="n">np</span><span class="o">::</span><span class="n">ndarray</span> <span class="n">example_tuple</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">array</span><span class="p">(</span><span class="n">tu</span><span class="p">);</span>
</pre></div>
</div>
<p>Let&#8217;s now try the same with a list. We create an empty list, add an element using the append method, and as before, call the array method</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">list</span> <span class="n">l</span> <span class="p">;</span>
<span class="n">l</span><span class="p">.</span><span class="n">append</span><span class="p">(</span><span class="sc">&#39;a&#39;</span><span class="p">)</span> <span class="p">;</span>
<span class="n">np</span><span class="o">::</span><span class="n">ndarray</span> <span class="n">example_list</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">array</span> <span class="p">(</span><span class="n">l</span><span class="p">)</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">list</span> <span class="n">l</span><span class="p">;</span>
<span class="n">l</span><span class="p">.</span><span class="n">append</span><span class="p">(</span><span class="sc">&#39;a&#39;</span><span class="p">);</span>
<span class="n">np</span><span class="o">::</span><span class="n">ndarray</span> <span class="n">example_list</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">array</span> <span class="p">(</span><span class="n">l</span><span class="p">);</span>
</pre></div>
</div>
<p>Optionally, we can also specify a dtype for the array</p>
@@ -102,18 +102,18 @@ ndarrays can also be created from arbitrary python sequences as well as from dat
</div>
<p>We can also create an array by supplying data arrays and a few other parameters.</p>
<p>First,create an integer array</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="kt">int</span> <span class="n">data</span><span class="p">[]</span> <span class="o">=</span> <span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">}</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre><span class="kt">int</span> <span class="n">data</span><span class="p">[]</span> <span class="o">=</span> <span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">};</span>
</pre></div>
</div>
<p>Create a shape, and strides, needed by the function</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">tuple</span> <span class="n">shape</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="p">;</span>
<span class="n">p</span><span class="o">::</span><span class="n">tuple</span> <span class="n">stride</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">))</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">tuple</span> <span class="n">shape</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">5</span><span class="p">);</span>
<span class="n">p</span><span class="o">::</span><span class="n">tuple</span> <span class="n">stride</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
</pre></div>
</div>
<p>Here, shape is (4,) , and the stride is <cite>sizeof(int)`</cite>.
A stride is the number of bytes that must be traveled to get to the next desired element while constructing the ndarray.</p>
<p>The function also needs an owner, to keep track of the data array passed. Passing none is dangerous</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">object</span> <span class="n">own</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">object</span> <span class="n">own</span><span class="p">;</span>
</pre></div>
</div>
<p>The from_data function takes the data array, datatype,shape,stride and owner as arguments and returns an ndarray</p>
@@ -121,7 +121,8 @@ A stride is the number of bytes that must be traveled to get to the next desired
</pre></div>
</div>
<p>Now let&#8217;s print the ndarray we created</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Single dimensional array ::&quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="o">&lt;&lt;</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span> <span class="o">&lt;</span> <span class="kt">char</span> <span class="k">const</span> <span class="o">*</span> <span class="o">&gt;</span> <span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">data_ex</span><span class="p">))</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Single dimensional array ::&quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span>
<span class="o">&lt;&lt;</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o">&lt;</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*&gt;</span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">data_ex</span><span class="p">))</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
</pre></div>
</div>
<p>Let&#8217;s make it a little more interesting. Lets make an 3x2 ndarray from a multi-dimensional array using non-unit strides</p>
@@ -131,8 +132,8 @@ A stride is the number of bytes that must be traveled to get to the next desired
</div>
<p>Now let&#8217;s create an array of 3x2 elements, picking the first and third elements from each row . For that, the shape will be 3x2.
The strides will be 4x2 i.e. 4 bytes to go to the next desired row, and 2 bytes to go to the next desired column</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">shape</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">)</span> <span class="p">;</span>
<span class="n">stride</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">uint8_t</span><span class="p">)</span><span class="o">*</span><span class="mi">2</span><span class="p">,</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">uint8_t</span><span class="p">))</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">shape</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
<span class="n">stride</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">uint8_t</span><span class="p">)</span><span class="o">*</span><span class="mi">2</span><span class="p">,</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">uint8_t</span><span class="p">));</span>
</pre></div>
</div>
<p>Get the numpy dtype for the built-in 8-bit integer data type</p>
@@ -142,17 +143,25 @@ The strides will be 4x2 i.e. 4 bytes to go to the next desired row, and 2 bytes
<p>Now lets first create and print out the ndarray as is.
Notice how we can pass the shape and strides in the function directly, as well as the owner. The last part can be done because we don&#8217;t have any use to
manipulate the &#8220;owner&#8221; object</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">np</span><span class="o">::</span><span class="n">ndarray</span> <span class="n">mul_data_ex</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">from_data</span><span class="p">(</span><span class="n">mul_data</span><span class="p">,</span><span class="n">dt1</span><span class="p">,</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">),</span><span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="mi">1</span><span class="p">),</span><span class="n">p</span><span class="o">::</span><span class="n">object</span><span class="p">());</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Original multi dimensional array :: &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="o">&lt;&lt;</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span> <span class="o">&lt;</span> <span class="kt">char</span> <span class="k">const</span> <span class="o">*</span> <span class="o">&gt;</span> <span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">mul_data_ex</span><span class="p">))</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">np</span><span class="o">::</span><span class="n">ndarray</span> <span class="n">mul_data_ex</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">from_data</span><span class="p">(</span><span class="n">mul_data</span><span class="p">,</span> <span class="n">dt1</span><span class="p">,</span>
<span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">),</span>
<span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="mi">1</span><span class="p">),</span>
<span class="n">p</span><span class="o">::</span><span class="n">object</span><span class="p">());</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Original multi dimensional array :: &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span>
<span class="o">&lt;&lt;</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o">&lt;</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*&gt;</span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">mul_data_ex</span><span class="p">))</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
</pre></div>
</div>
<p>Now create the new ndarray using the shape and strides and print out the array we created using non-unit strides</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">mul_data_ex</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">from_data</span><span class="p">(</span><span class="n">mul_data</span><span class="p">,</span><span class="n">dt1</span><span class="p">,</span> <span class="n">shape</span><span class="p">,</span><span class="n">stride</span><span class="p">,</span><span class="n">p</span><span class="o">::</span><span class="n">object</span><span class="p">());</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Selective multidimensional array :: &quot;</span><span class="o">&lt;&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="o">&lt;&lt;</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span> <span class="o">&lt;</span> <span class="kt">char</span> <span class="k">const</span> <span class="o">*</span> <span class="o">&gt;</span> <span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">mul_data_ex</span><span class="p">))</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="p">;</span>
<div class="highlight-c++"><div class="highlight"><pre> <span class="n">mul_data_ex</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">from_data</span><span class="p">(</span><span class="n">mul_data</span><span class="p">,</span> <span class="n">dt1</span><span class="p">,</span> <span class="n">shape</span><span class="p">,</span> <span class="n">stride</span><span class="p">,</span> <span class="n">p</span><span class="o">::</span><span class="n">object</span><span class="p">());</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Selective multidimensional array :: &quot;</span><span class="o">&lt;&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">endl</span>
<span class="o">&lt;&lt;</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o">&lt;</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*&gt;</span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">mul_data_ex</span><span class="p">))</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Note : The from_data method will throw &#8220;error_already_set&#8221; if the number of elements dictated by the shape and the corresponding strides don&#8217;t match</p>
<p>}</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The from_data method will throw <tt class="docutils literal"><span class="pre">error_already_set</span></tt> if the number of elements dictated by the shape and the corresponding strides don&#8217;t match.</p>
</div>
</div>