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Struct, Memoryview, Deque
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gto76 committed May 7, 2024
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24 changes: 12 additions & 12 deletions README.md
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Expand Up @@ -1998,7 +1998,8 @@ Struct

```python
from struct import pack, unpack
<bytes> = pack('<format>', <el_1> [, ...]) # Packages arguments. Can raise struct.error.

<bytes> = pack('<format>', <el_1> [, ...]) # Packs objects according to format string.
<tuple> = unpack('<format>', <bytes>) # Use iter_unpack() to get iterator of tuples.
```

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Memory View
-----------
* **A sequence object that points to the memory of another bytes-like object.**
* **Each element can reference a single or multiple consecutive bytes, depending on format.**
* **Order and number of elements can be changed with slicing.**
* **Casting only works between char and other types and uses system's sizes.**
* **Byte order is always determined by the system.**
**A sequence object that points to the memory of another bytes-like object. Each element can reference a single or multiple consecutive bytes, depending on format. Order and number of elements can be changed with slicing.**

```python
<mview> = memoryview(<bytes/bytearray/array>) # Immutable if bytes, else mutable.
<real> = <mview>[index] # Returns an int or a float.
<mview> = <mview>[<slice>] # Mview with rearranged elements.
<mview> = <mview>.cast('<typecode>') # Casts memoryview to the new format.
<mview>.release() # Releases memory buffer of target object.
<mview> = <mview>[<slice>] # Returns mview with rearranged elements.
<mview> = <mview>.cast('<typecode>') # Only works between b/B/c and other types.
<mview>.release() # Releases memory buffer of the base object.
```

```python
<bytes> = bytes(<mview>) # Returns a new bytes object.
<bytes> = <bytes>.join(<coll_of_mviews>) # Joins mviews using bytes object as sep.
<bytes> = <bytes>.join(<coll_of_mviews>) # Joins mviews using bytes as a separator.
<array> = array('<typecode>', <mview>) # Treats mview as a sequence of numbers.
<file>.write(<mview>) # Writes mview to the binary file.
```
Expand All @@ -2088,11 +2085,14 @@ Deque

```python
from collections import deque
```

```python
<deque> = deque(<collection>) # Also `maxlen=None`.
<deque>.appendleft(<el>) # Opposite element is dropped if full.
<deque>.extendleft(<collection>) # Collection gets reversed.
<el> = <deque>.popleft() # Raises IndexError if empty.
<deque>.extendleft(<collection>) # Passed collection gets reversed.
<deque>.rotate(n=1) # Rotates elements to the right.
<el> = <deque>.popleft() # Raises IndexError if empty.
```


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34 changes: 15 additions & 19 deletions index.html
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Expand Up @@ -54,7 +54,7 @@

<body>
<header>
<aside>May 5, 2024</aside>
<aside>May 7, 2024</aside>
<a href="https://gto76.github.io" rel="author">Jure Šorn</a>
</header>

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<li><strong>Module that performs conversions between a sequence of numbers and a bytes object.</strong></li>
<li><strong>System’s type sizes, byte order, and alignment rules are used by default.</strong></li>
</ul><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> struct <span class="hljs-keyword">import</span> pack, unpack
&lt;bytes&gt; = pack(<span class="hljs-string">'&lt;format&gt;'</span>, &lt;el_1&gt; [, ...]) <span class="hljs-comment"># Packages arguments. Can raise struct.error.</span>

&lt;bytes&gt; = pack(<span class="hljs-string">'&lt;format&gt;'</span>, &lt;el_1&gt; [, ...]) <span class="hljs-comment"># Packs objects according to format string.</span>
&lt;tuple&gt; = unpack(<span class="hljs-string">'&lt;format&gt;'</span>, &lt;bytes&gt;) <span class="hljs-comment"># Use iter_unpack() to get iterator of tuples.</span>
</code></pre></div>

Expand Down Expand Up @@ -1695,22 +1696,16 @@ <h3 id="format-2">Format</h3><div><h4 id="forstandardtypesizesandmanualalignment
<pre><code class="python language-python hljs">&lt;bytes&gt; = bytes(&lt;array&gt;) <span class="hljs-comment"># Converts array to a bytes object.</span>
&lt;file&gt;.write(&lt;array&gt;) <span class="hljs-comment"># Writes array to the binary file.</span>
</code></pre>
<div><h2 id="memoryview"><a href="#memoryview" name="memoryview">#</a>Memory View</h2><ul>
<li><strong>A sequence object that points to the memory of another bytes-like object.</strong></li>
<li><strong>Each element can reference a single or multiple consecutive bytes, depending on format.</strong></li>
<li><strong>Order and number of elements can be changed with slicing.</strong></li>
<li><strong>Casting only works between char and other types and uses system's sizes.</strong></li>
<li><strong>Byte order is always determined by the system.</strong></li>
</ul><pre><code class="python language-python hljs">&lt;mview&gt; = memoryview(&lt;bytes/bytearray/array&gt;) <span class="hljs-comment"># Immutable if bytes, else mutable.</span>
<div><h2 id="memoryview"><a href="#memoryview" name="memoryview">#</a>Memory View</h2><p><strong>A sequence object that points to the memory of another bytes-like object. Each element can reference a single or multiple consecutive bytes, depending on format. Order and number of elements can be changed with slicing.</strong></p><pre><code class="python language-python hljs">&lt;mview&gt; = memoryview(&lt;bytes/bytearray/array&gt;) <span class="hljs-comment"># Immutable if bytes, else mutable.</span>
&lt;real&gt; = &lt;mview&gt;[index] <span class="hljs-comment"># Returns an int or a float.</span>
&lt;mview&gt; = &lt;mview&gt;[&lt;slice&gt;] <span class="hljs-comment"># Mview with rearranged elements.</span>
&lt;mview&gt; = &lt;mview&gt;.cast(<span class="hljs-string">'&lt;typecode&gt;'</span>) <span class="hljs-comment"># Casts memoryview to the new format.</span>
&lt;mview&gt;.release() <span class="hljs-comment"># Releases memory buffer of target object.</span>
&lt;mview&gt; = &lt;mview&gt;[&lt;slice&gt;] <span class="hljs-comment"># Returns mview with rearranged elements.</span>
&lt;mview&gt; = &lt;mview&gt;.cast(<span class="hljs-string">'&lt;typecode&gt;'</span>) <span class="hljs-comment"># Only works between b/B/c and other types.</span>
&lt;mview&gt;.release() <span class="hljs-comment"># Releases memory buffer of the base object.</span>
</code></pre></div>


<pre><code class="python language-python hljs">&lt;bytes&gt; = bytes(&lt;mview&gt;) <span class="hljs-comment"># Returns a new bytes object.</span>
&lt;bytes&gt; = &lt;bytes&gt;.join(&lt;coll_of_mviews&gt;) <span class="hljs-comment"># Joins mviews using bytes object as sep.</span>
&lt;bytes&gt; = &lt;bytes&gt;.join(&lt;coll_of_mviews&gt;) <span class="hljs-comment"># Joins mviews using bytes as a separator.</span>
&lt;array&gt; = array(<span class="hljs-string">'&lt;typecode&gt;'</span>, &lt;mview&gt;) <span class="hljs-comment"># Treats mview as a sequence of numbers.</span>
&lt;file&gt;.write(&lt;mview&gt;) <span class="hljs-comment"># Writes mview to the binary file.</span>
</code></pre>
Expand All @@ -1719,14 +1714,15 @@ <h3 id="format-2">Format</h3><div><h4 id="forstandardtypesizesandmanualalignment
&lt;str&gt; = &lt;mview&gt;.hex() <span class="hljs-comment"># Returns hex pairs. Accepts `sep=&lt;str&gt;`.</span>
</code></pre>
<div><h2 id="deque"><a href="#deque" name="deque">#</a>Deque</h2><p><strong>A thread-safe list with efficient appends and pops from either side. Pronounced "deck".</strong></p><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> collections <span class="hljs-keyword">import</span> deque
&lt;deque&gt; = deque(&lt;collection&gt;) <span class="hljs-comment"># Also `maxlen=None`.</span>
&lt;deque&gt;.appendleft(&lt;el&gt;) <span class="hljs-comment"># Opposite element is dropped if full.</span>
&lt;deque&gt;.extendleft(&lt;collection&gt;) <span class="hljs-comment"># Collection gets reversed.</span>
&lt;el&gt; = &lt;deque&gt;.popleft() <span class="hljs-comment"># Raises IndexError if empty.</span>
&lt;deque&gt;.rotate(n=<span class="hljs-number">1</span>) <span class="hljs-comment"># Rotates elements to the right.</span>
</code></pre></div>


<pre><code class="python language-python hljs">&lt;deque&gt; = deque(&lt;collection&gt;) <span class="hljs-comment"># Also `maxlen=None`.</span>
&lt;deque&gt;.appendleft(&lt;el&gt;) <span class="hljs-comment"># Opposite element is dropped if full.</span>
&lt;deque&gt;.extendleft(&lt;collection&gt;) <span class="hljs-comment"># Passed collection gets reversed.</span>
&lt;deque&gt;.rotate(n=<span class="hljs-number">1</span>) <span class="hljs-comment"># Rotates elements to the right.</span>
&lt;el&gt; = &lt;deque&gt;.popleft() <span class="hljs-comment"># Raises IndexError if empty.</span>
</code></pre>
<div><h2 id="threading"><a href="#threading" name="threading">#</a>Threading</h2><p><strong>CPython interpreter can only run a single thread at a time. Using multiple threads won't result in a faster execution, unless at least one of the threads contains an I/O operation.</strong></p><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> threading <span class="hljs-keyword">import</span> Thread, Timer, RLock, Semaphore, Event, Barrier
<span class="hljs-keyword">from</span> concurrent.futures <span class="hljs-keyword">import</span> ThreadPoolExecutor, as_completed
</code></pre></div>
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<footer>
<aside>May 5, 2024</aside>
<aside>May 7, 2024</aside>
<a href="https://gto76.github.io" rel="author">Jure Šorn</a>
</footer>

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