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python-cheatsheet
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MemoryView

pull/44/head
Jure Šorn 5 years ago
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3 changed files with 53 additions and 14 deletions
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  1. 25
      README.md
  2. 31
      index.html
  3. 11
      parse.js

25
README.md
View File

@ -1943,11 +1943,26 @@ from array import array
Memory View Memory View
----------- -----------
**Used for accessing the internal data of an object that supports the buffer protocol.**
* **Memory View is a seqence that points to the memory of bytes, bytearray or array objects.**
* **Each element can reference a single or multiple consecutive bytes.**
* **Referenced elements can be narrowed down with slicing.**
```python ```python
<mview> = memoryview(<bytes> / <bytearray> / <array>)
<mview>.release() # Releases the buffer.
<mview> = memoryview(<bytes/bytearray/array>)
<num> = <mview>[<index>] # Can be int or float.
<mview> = <mview>[<slice>] # Mview with rearanged elements.
<mview> = <mview>.cast('<typecode>') # Cast a memoryview to a new format.
<mview>.release() # Releases the buffer.
```
```python
<bin_file>.write(<mview>)
<bytes> = bytes(<mview>) # Or: <mview>.tobytes()
<bytes> = <bytes>.join(<coll_of_mviews>) # Joins mviews using bytes object as sep.
<list> = list(<mview>) # Returns numbers. Or: <mview>.tolist()
<str> = str(<mview>, 'utf-8') # Or: <bytes>.decode('utf-8')
<int> = int.from_bytes(<mview>, byteorder='big|little', signed=False)
'<hex>' = <mview>.hex()
``` ```
@ -2217,7 +2232,7 @@ def printer():
reader(adder(printer())) # 100, 101, ..., 109 reader(adder(printer())) # 100, 101, ..., 109
``` ```
<br><br>
<br>
Libraries Libraries
========= =========
@ -2253,7 +2268,7 @@ Table
```python ```python
# $ pip3 install tabulate # $ pip3 install tabulate
import csv, tabulate import csv, tabulate
with open(<filename>, encoding='utf-8', newline='') as file:
with open('test.csv', encoding='utf-8', newline='') as file:
rows = csv.reader(file) rows = csv.reader(file)
header = [a.title() for a in next(rows)] header = [a.title() for a in next(rows)]
table = tabulate.tabulate(rows, header) table = tabulate.tabulate(rows, header)

31
index.html
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@ -1394,16 +1394,16 @@ value = args.&lt;name&gt;
<li><strong><code class="python hljs"><span class="hljs-string">'a+'</span></code> - Read and write from the end.</strong></li> <li><strong><code class="python hljs"><span class="hljs-string">'a+'</span></code> - Read and write from the end.</strong></li>
<li><strong><code class="python hljs"><span class="hljs-string">'t'</span></code> - Text mode (default).</strong></li> <li><strong><code class="python hljs"><span class="hljs-string">'t'</span></code> - Text mode (default).</strong></li>
<li><strong><code class="python hljs"><span class="hljs-string">'b'</span></code> - Binary mode.</strong></li> <li><strong><code class="python hljs"><span class="hljs-string">'b'</span></code> - Binary mode.</strong></li>
</ul><div><h3 id="exceptions-1">Exceptions</h3><ul>
</ul></div><div><h3 id="exceptions-1">Exceptions</h3><ul>
<li><strong><code class="python hljs"><span class="hljs-string">'FileNotFoundError'</span></code> can be risen when reading with <code class="python hljs"><span class="hljs-string">'r'</span></code> or <code class="python hljs"><span class="hljs-string">'r+'</span></code>.</strong></li> <li><strong><code class="python hljs"><span class="hljs-string">'FileNotFoundError'</span></code> can be risen when reading with <code class="python hljs"><span class="hljs-string">'r'</span></code> or <code class="python hljs"><span class="hljs-string">'r+'</span></code>.</strong></li>
<li><strong><code class="python hljs"><span class="hljs-string">'FileExistsError'</span></code> can be risen when writing with <code class="python hljs"><span class="hljs-string">'x'</span></code>.</strong></li> <li><strong><code class="python hljs"><span class="hljs-string">'FileExistsError'</span></code> can be risen when writing with <code class="python hljs"><span class="hljs-string">'x'</span></code>.</strong></li>
<li><strong><code class="python hljs"><span class="hljs-string">'IsADirectoryError'</span></code> and <code class="python hljs"><span class="hljs-string">'PermissionError'</span></code> can be risen by any.</strong></li> <li><strong><code class="python hljs"><span class="hljs-string">'IsADirectoryError'</span></code> and <code class="python hljs"><span class="hljs-string">'PermissionError'</span></code> can be risen by any.</strong></li>
<li><strong><code class="python hljs"><span class="hljs-string">'OSError'</span></code> is the parent class of all listed exceptions.</strong></li> <li><strong><code class="python hljs"><span class="hljs-string">'OSError'</span></code> is the parent class of all listed exceptions.</strong></li>
</ul><div><h3 id="file">File</h3><pre><code class="python language-python hljs">&lt;file&gt;.seek(<span class="hljs-number">0</span>) <span class="hljs-comment"># Moves to the start of the file.</span>
</ul></div><div><h3 id="file">File</h3><pre><code class="python language-python hljs">&lt;file&gt;.seek(<span class="hljs-number">0</span>) <span class="hljs-comment"># Moves to the start of the file.</span>
&lt;file&gt;.seek(offset) <span class="hljs-comment"># Moves 'offset' chars/bytes from the start.</span> &lt;file&gt;.seek(offset) <span class="hljs-comment"># Moves 'offset' chars/bytes from the start.</span>
&lt;file&gt;.seek(<span class="hljs-number">0</span>, <span class="hljs-number">2</span>) <span class="hljs-comment"># Moves to the end of the file.</span> &lt;file&gt;.seek(<span class="hljs-number">0</span>, <span class="hljs-number">2</span>) <span class="hljs-comment"># Moves to the end of the file.</span>
&lt;bin_file&gt;.seek(±offset, &lt;anchor&gt;) <span class="hljs-comment"># Anchor: 0 start, 1 current pos., 2 end.</span> &lt;bin_file&gt;.seek(±offset, &lt;anchor&gt;) <span class="hljs-comment"># Anchor: 0 start, 1 current pos., 2 end.</span>
</code></pre></div></div></div>
</code></pre></div>
@ -1724,11 +1724,26 @@ db = connector.connect(host=&lt;str&gt;, user=&lt;str&gt;, password=&lt;str&gt;,
</code></pre></div> </code></pre></div>
<div><h2 id="memoryview"><a href="#memoryview" name="memoryview">#</a>Memory View</h2><p><strong>Used for accessing the internal data of an object that supports the buffer protocol.</strong></p><pre><code class="python language-python hljs">&lt;mview&gt; = memoryview(&lt;bytes&gt; / &lt;bytearray&gt; / &lt;array&gt;)
&lt;mview&gt;.release() <span class="hljs-comment"># Releases the buffer.</span>
<div><h2 id="memoryview"><a href="#memoryview" name="memoryview">#</a>Memory View</h2><ul>
<li><strong>Memory View is a seqence that points to the memory of bytes, bytearray or array objects.</strong></li>
<li><strong>Each element can reference a single or multiple consecutive bytes.</strong></li>
<li><strong>Referenced elements can be narrowed down with slicing.</strong></li>
</ul><pre><code class="python language-python hljs">&lt;mview&gt; = memoryview(&lt;bytes/bytearray/array&gt;)
&lt;num&gt; = &lt;mview&gt;[&lt;index&gt;] <span class="hljs-comment"># Can be int or float.</span>
&lt;mview&gt; = &lt;mview&gt;[&lt;slice&gt;] <span class="hljs-comment"># Mview with rearanged elements.</span>
&lt;mview&gt; = &lt;mview&gt;.cast(<span class="hljs-string">'&lt;typecode&gt;'</span>) <span class="hljs-comment"># Cast a memoryview to a new format.</span>
&lt;mview&gt;.release() <span class="hljs-comment"># Releases the buffer.</span>
</code></pre></div> </code></pre></div>
<pre><code class="python language-python hljs">&lt;bin_file&gt;.write(&lt;mview&gt;)
&lt;bytes&gt; = bytes(&lt;mview&gt;) <span class="hljs-comment"># Or: &lt;mview&gt;.tobytes()</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;list&gt; = list(&lt;mview&gt;) <span class="hljs-comment"># Returns numbers. Or: &lt;mview&gt;.tolist()</span>
&lt;str&gt; = str(&lt;mview&gt;, <span class="hljs-string">'utf-8'</span>) <span class="hljs-comment"># Or: &lt;bytes&gt;.decode('utf-8')</span>
&lt;int&gt; = int.from_bytes(&lt;mview&gt;, byteorder=<span class="hljs-string">'big|little'</span>, signed=<span class="hljs-keyword">False</span>)
<span class="hljs-string">'&lt;hex&gt;'</span> = &lt;mview&gt;.hex()
</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 <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;, maxlen=<span class="hljs-keyword">None</span>) &lt;deque&gt; = deque(&lt;collection&gt;, maxlen=<span class="hljs-keyword">None</span>)
</code></pre></div> </code></pre></div>
@ -1925,8 +1940,8 @@ ValueError: malformed node or string
reader(adder(printer())) <span class="hljs-comment"># 100, 101, ..., 109</span> reader(adder(printer())) <span class="hljs-comment"># 100, 101, ..., 109</span>
</code></pre></div> </code></pre></div>
<p><br><br></p>
<div class="pagebreak"></div><div><h1 id="libraries">Libraries</h1><div><h2 id="progressbar"><a href="#progressbar" name="progressbar">#</a>Progress Bar</h2><pre><code class="python language-python hljs"><span class="hljs-comment"># $ pip3 install tqdm</span>
<p><br></p>
<div><h1 id="libraries">Libraries</h1><div><h2 id="progressbar"><a href="#progressbar" name="progressbar">#</a>Progress Bar</h2><pre><code class="python language-python hljs"><span class="hljs-comment"># $ pip3 install tqdm</span>
<span class="hljs-keyword">from</span> tqdm <span class="hljs-keyword">import</span> tqdm <span class="hljs-keyword">from</span> tqdm <span class="hljs-keyword">import</span> tqdm
<span class="hljs-keyword">from</span> time <span class="hljs-keyword">import</span> sleep <span class="hljs-keyword">from</span> time <span class="hljs-keyword">import</span> sleep
<span class="hljs-keyword">for</span> el <span class="hljs-keyword">in</span> tqdm([<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>]): <span class="hljs-keyword">for</span> el <span class="hljs-keyword">in</span> tqdm([<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>]):
@ -1946,7 +1961,7 @@ pyplot.clf() <span class="hljs-comment"># Clears figur
<div><h2 id="table"><a href="#table" name="table">#</a>Table</h2><div><h4 id="printsacsvfileasanasciitable">Prints a CSV file as an ASCII table:</h4><pre><code class="python language-python hljs"><span class="hljs-comment"># $ pip3 install tabulate</span> <div><h2 id="table"><a href="#table" name="table">#</a>Table</h2><div><h4 id="printsacsvfileasanasciitable">Prints a CSV file as an ASCII table:</h4><pre><code class="python language-python hljs"><span class="hljs-comment"># $ pip3 install tabulate</span>
<span class="hljs-keyword">import</span> csv, tabulate <span class="hljs-keyword">import</span> csv, tabulate
<span class="hljs-keyword">with</span> open(&lt;filename&gt;, encoding=<span class="hljs-string">'utf-8'</span>, newline=<span class="hljs-string">''</span>) <span class="hljs-keyword">as</span> file:
<span class="hljs-keyword">with</span> open(<span class="hljs-string">'test.csv'</span>, encoding=<span class="hljs-string">'utf-8'</span>, newline=<span class="hljs-string">''</span>) <span class="hljs-keyword">as</span> file:
rows = csv.reader(file) rows = csv.reader(file)
header = [a.title() <span class="hljs-keyword">for</span> a <span class="hljs-keyword">in</span> next(rows)] header = [a.title() <span class="hljs-keyword">for</span> a <span class="hljs-keyword">in</span> next(rows)]
table = tabulate.tabulate(rows, header) table = tabulate.tabulate(rows, header)

11
parse.js
View File

@ -303,7 +303,8 @@ function highlightCode() {
fixClasses(); fixClasses();
fixHighlights(); fixHighlights();
preventPageBreaks(); preventPageBreaks();
insertPageBreak();
fixPageBreaks();
// insertPageBreak();
} }
function setApaches(elements) { function setApaches(elements) {
@ -338,6 +339,14 @@ function preventPageBreaks() {
}); });
} }
function fixPageBreaks() {
const fileDiv = $('#file').parent()
const modesDiv = $('#file').parent().parent().parent()
modesDiv.after(fileDiv)
const exceptDiv = $('#exceptions-1').parent()
modesDiv.after(exceptDiv)
}
function insertPageBreak() { function insertPageBreak() {
$('<div class="pagebreak"></div>').insertBefore($('#libraries').parent()) $('<div class="pagebreak"></div>').insertBefore($('#libraries').parent())
} }

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