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python-cheatsheet
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OS Commands, Operator

pull/74/merge
Jure Šorn 2 years ago
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  1. 26
      README.md
  2. 44
      index.html

26
README.md
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@ -1610,7 +1610,7 @@ def write_to_file(filename, text):
Paths
-----
```python
from os import getcwd, path, listdir
from os import getcwd, path, listdir, scandir
from glob import glob
```
@ -1640,10 +1640,6 @@ from glob import glob
### DirEntry
**Using scandir() instead of listdir() can significantly increase the performance of code that also needs file type information.**
```python
from os import scandir
```
```python
<iter> = scandir(path='.') # Returns DirEntry objects located at path.
<str> = <DirEntry>.path # Returns whole path as a string.
@ -1689,14 +1685,14 @@ from pathlib import Path
OS Commands
-----------
```python
import os, shutil, subprocess
```
### Files and Directories
* **Paths can be either strings, Paths or DirEntry objects.**
* **Functions report OS related errors by raising either OSError or one of its [subclasses](#exceptions-1).**
```python
import os, shutil
```
```python
os.chdir(<path>) # Changes the current working directory.
os.mkdir(<path>, mode=0o777) # Creates a directory. Mode is in octal.
@ -1721,14 +1717,14 @@ shutil.rmtree(<path>) # Deletes the directory.
### Shell Commands
```python
import os
<str> = os.popen('<shell_command>').read()
<pipe> = os.popen('<command>') # Executes command in sh/cmd and returns its stdout pipe.
<str> = <pipe>.read() # Waits for EOF and returns result. Also readline/s().
<int> = <pipe>.close() # Closes the pipe. Returns None on success, int on error.
```
#### Sends '1 + 1' to the basic calculator and captures its output:
```python
>>> from subprocess import run
>>> run('bc', input='1 + 1\n', capture_output=True, text=True)
>>> subprocess.run('bc', input='1 + 1\n', capture_output=True, text=True)
CompletedProcess(args='bc', returncode=0, stdout='2\n', stderr='')
```
@ -1736,7 +1732,7 @@ CompletedProcess(args='bc', returncode=0, stdout='2\n', stderr='')
```python
>>> from shlex import split
>>> os.popen('echo 1 + 1 > test.in')
>>> run(split('bc -s'), stdin=open('test.in'), stdout=open('test.out', 'w'))
>>> subprocess.run(split('bc -s'), stdin=open('test.in'), stdout=open('test.out', 'w'))
CompletedProcess(args=['bc', '-s'], returncode=0)
>>> open('test.out').read()
'2\n'
@ -2148,7 +2144,7 @@ import operator as op
<el> = op.add/sub/mul/truediv/floordiv/mod(<el>, <el>) # +, -, *, /, //, %
<int/set> = op.and_/or_/xor(<int/set>, <int/set>) # &, |, ^
<bool> = op.eq/ne/lt/le/gt/ge(<sortable>, <sortable>) # ==, !=, <, <=, >, >=
<func> = op.itemgetter/attrgetter/methodcaller(<el>) # [index/key], .<str>, .<str>()
<func> = op.itemgetter/attrgetter/methodcaller(<obj>) # [index/key], .name, .name()
```
```python

44
index.html
View File

@ -54,7 +54,7 @@
<body>
<header>
<aside>April 15, 2022</aside>
<aside>April 18, 2022</aside>
<a href="https://gto76.github.io" rel="author">Jure Šorn</a>
</header>
@ -1373,7 +1373,7 @@ value = args.&lt;name&gt;
file.write(text)
</code></pre></div>
<div><h2 id="paths"><a href="#paths" name="paths">#</a>Paths</h2><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> os <span class="hljs-keyword">import</span> getcwd, path, listdir
<div><h2 id="paths"><a href="#paths" name="paths">#</a>Paths</h2><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> os <span class="hljs-keyword">import</span> getcwd, path, listdir, scandir
<span class="hljs-keyword">from</span> glob <span class="hljs-keyword">import</span> glob
</code></pre></div>
@ -1392,15 +1392,13 @@ value = args.&lt;name&gt;
&lt;bool&gt; = path.isfile(&lt;path&gt;) <span class="hljs-comment"># Or: &lt;DirEntry/Path&gt;.is_file()</span>
&lt;bool&gt; = path.isdir(&lt;path&gt;) <span class="hljs-comment"># Or: &lt;DirEntry/Path&gt;.is_dir()</span>
</code></pre>
<div><h3 id="direntry">DirEntry</h3><p><strong>Using scandir() instead of listdir() can significantly increase the performance of code that also needs file type information.</strong></p><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> os <span class="hljs-keyword">import</span> scandir
</code></pre></div>
<pre><code class="python language-python hljs">&lt;iter&gt; = scandir(path=<span class="hljs-string">'.'</span>) <span class="hljs-comment"># Returns DirEntry objects located at path.</span>
<div><h3 id="direntry">DirEntry</h3><p><strong>Using scandir() instead of listdir() can significantly increase the performance of code that also needs file type information.</strong></p><pre><code class="python language-python hljs">&lt;iter&gt; = scandir(path=<span class="hljs-string">'.'</span>) <span class="hljs-comment"># Returns DirEntry objects located at path.</span>
&lt;str&gt; = &lt;DirEntry&gt;.path <span class="hljs-comment"># Returns whole path as a string.</span>
&lt;str&gt; = &lt;DirEntry&gt;.name <span class="hljs-comment"># Returns final component as a string.</span>
&lt;file&gt; = open(&lt;DirEntry&gt;) <span class="hljs-comment"># Opens the file and returns a file object.</span>
</code></pre>
</code></pre></div>
<div><h3 id="pathobject">Path Object</h3><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> pathlib <span class="hljs-keyword">import</span> Path
</code></pre></div>
@ -1424,18 +1422,18 @@ value = args.&lt;name&gt;
<pre><code class="python language-python hljs">&lt;str&gt; = str(&lt;Path&gt;) <span class="hljs-comment"># Returns path as a string.</span>
&lt;file&gt; = open(&lt;Path&gt;) <span class="hljs-comment"># Opens the file and returns a file object.</span>
</code></pre>
<div><h2 id="oscommands"><a href="#oscommands" name="oscommands">#</a>OS Commands</h2><div><h3 id="filesanddirectories">Files and Directories</h3><ul>
<div><h2 id="oscommands"><a href="#oscommands" name="oscommands">#</a>OS Commands</h2><pre><code class="python language-python hljs"><span class="hljs-keyword">import</span> os, shutil, subprocess
</code></pre></div>
<div><h3 id="filesanddirectories">Files and Directories</h3><ul>
<li><strong>Paths can be either strings, Paths or DirEntry objects.</strong></li>
<li><strong>Functions report OS related errors by raising either OSError or one of its <a href="#exceptions-1">subclasses</a>.</strong></li>
</ul><pre><code class="python language-python hljs"><span class="hljs-keyword">import</span> os, shutil
</code></pre></div></div>
<pre><code class="python language-python hljs">os.chdir(&lt;path&gt;) <span class="hljs-comment"># Changes the current working directory.</span>
</ul><pre><code class="python language-python hljs">os.chdir(&lt;path&gt;) <span class="hljs-comment"># Changes the current working directory.</span>
os.mkdir(&lt;path&gt;, mode=<span class="hljs-number">0o777</span>) <span class="hljs-comment"># Creates a directory. Mode is in octal.</span>
os.makedirs(&lt;path&gt;, mode=<span class="hljs-number">0o777</span>) <span class="hljs-comment"># Creates all directories in the path.</span>
</code></pre>
</code></pre></div>
<pre><code class="python language-python hljs">shutil.copy(from, to) <span class="hljs-comment"># Copies the file. 'to' can exist or be a dir.</span>
shutil.copytree(from, to) <span class="hljs-comment"># Copies the directory. 'to' must not exist.</span>
</code></pre>
@ -1446,18 +1444,18 @@ os.replace(from, to) <span class="hljs-comment"># Same, but overw
os.rmdir(&lt;path&gt;) <span class="hljs-comment"># Deletes the empty directory.</span>
shutil.rmtree(&lt;path&gt;) <span class="hljs-comment"># Deletes the directory.</span>
</code></pre>
<div><h3 id="shellcommands">Shell Commands</h3><pre><code class="python language-python hljs"><span class="hljs-keyword">import</span> os
&lt;str&gt; = os.popen(<span class="hljs-string">'&lt;shell_command&gt;'</span>).read()
<div><h3 id="shellcommands">Shell Commands</h3><pre><code class="python language-python hljs">&lt;pipe&gt; = os.popen(<span class="hljs-string">'&lt;command&gt;'</span>) <span class="hljs-comment"># Executes command in sh/cmd and returns its stdout pipe.</span>
&lt;str&gt; = &lt;pipe&gt;.read() <span class="hljs-comment"># Waits for EOF and returns result. Also readline/s().</span>
&lt;int&gt; = &lt;pipe&gt;.close() <span class="hljs-comment"># Closes the pipe. Returns None on success, int on error.</span>
</code></pre></div>
<div><h4 id="sends11tothebasiccalculatorandcapturesitsoutput">Sends '1 + 1' to the basic calculator and captures its output:</h4><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span><span class="hljs-keyword">from</span> subprocess <span class="hljs-keyword">import</span> run
<span class="hljs-meta">&gt;&gt;&gt; </span>run(<span class="hljs-string">'bc'</span>, input=<span class="hljs-string">'1 + 1\n'</span>, capture_output=<span class="hljs-keyword">True</span>, text=<span class="hljs-keyword">True</span>)
<div><h4 id="sends11tothebasiccalculatorandcapturesitsoutput">Sends '1 + 1' to the basic calculator and captures its output:</h4><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>subprocess.run(<span class="hljs-string">'bc'</span>, input=<span class="hljs-string">'1 + 1\n'</span>, capture_output=<span class="hljs-keyword">True</span>, text=<span class="hljs-keyword">True</span>)
CompletedProcess(args=<span class="hljs-string">'bc'</span>, returncode=<span class="hljs-number">0</span>, stdout=<span class="hljs-string">'2\n'</span>, stderr=<span class="hljs-string">''</span>)
</code></pre></div>
<div><h4 id="sendstestintothebasiccalculatorrunninginstandardmodeandsavesitsoutputtotestout">Sends test.in to the basic calculator running in standard mode and saves its output to test.out:</h4><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span><span class="hljs-keyword">from</span> shlex <span class="hljs-keyword">import</span> split
<span class="hljs-meta">&gt;&gt;&gt; </span>os.popen(<span class="hljs-string">'echo 1 + 1 &gt; test.in'</span>)
<span class="hljs-meta">&gt;&gt;&gt; </span>run(split(<span class="hljs-string">'bc -s'</span>), stdin=open(<span class="hljs-string">'test.in'</span>), stdout=open(<span class="hljs-string">'test.out'</span>, <span class="hljs-string">'w'</span>))
<span class="hljs-meta">&gt;&gt;&gt; </span>subprocess.run(split(<span class="hljs-string">'bc -s'</span>), stdin=open(<span class="hljs-string">'test.in'</span>), stdout=open(<span class="hljs-string">'test.out'</span>, <span class="hljs-string">'w'</span>))
CompletedProcess(args=[<span class="hljs-string">'bc'</span>, <span class="hljs-string">'-s'</span>], returncode=<span class="hljs-number">0</span>)
<span class="hljs-meta">&gt;&gt;&gt; </span>open(<span class="hljs-string">'test.out'</span>).read()
<span class="hljs-string">'2\n'</span>
@ -1770,7 +1768,7 @@ CompletedProcess(args=[<span class="hljs-string">'bc'</span>, <span class="hljs-
&lt;el&gt; = op.add/sub/mul/truediv/floordiv/mod(&lt;el&gt;, &lt;el&gt;) <span class="hljs-comment"># +, -, *, /, //, %</span>
&lt;int/set&gt; = op.and_/or_/xor(&lt;int/set&gt;, &lt;int/set&gt;) <span class="hljs-comment"># &amp;, |, ^</span>
&lt;bool&gt; = op.eq/ne/lt/le/gt/ge(&lt;sortable&gt;, &lt;sortable&gt;) <span class="hljs-comment"># ==, !=, &lt;, &lt;=, &gt;, &gt;=</span>
&lt;func&gt; = op.itemgetter/attrgetter/methodcaller(&lt;el&gt;) <span class="hljs-comment"># [index/key], .&lt;str&gt;, .&lt;str&gt;()</span>
&lt;func&gt; = op.itemgetter/attrgetter/methodcaller(&lt;obj&gt;) <span class="hljs-comment"># [index/key], .name, .name()</span>
</code></pre></div>
@ -2889,7 +2887,7 @@ $ pyinstaller script.py --add-data '&lt;path&gt;:.' <span class="hljs-comment">
<footer>
<aside>April 15, 2022</aside>
<aside>April 18, 2022</aside>
<a href="https://gto76.github.io" rel="author">Jure Šorn</a>
</footer>

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