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python-cheatsheet
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SQLite example

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Jure Šorn 5 years ago
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      README.md
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README.md
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@ -1760,14 +1760,6 @@ db.close()
```
* **New database will be created if path doesn't exist.**
### Create
```python
>>> db.execute('create table t (a, b, c)')
>>> db.execute('insert into t values (1, 2, 3)')
>>> db.execute('select * from t').fetchall()
[(1, 2, 3)]
```
### Read
```python
cursor = db.execute('<query>')
@ -1783,6 +1775,12 @@ db.execute('<query>')
db.commit()
```
#### Or:
```python
with db:
db.execute('<query>')
```
### Placeholders
```python
db.execute('<query>', <list/tuple>) # Replaces '?'s in query with values.
@ -1791,6 +1789,16 @@ db.executemany('<query>', <coll_of_above>) # Runs execute() many times.
```
* **Passed values can be of type str, int, float, bytes, None, bool, datetime.date or datetime.datetme.**
### Example
```python
>>> db = sqlite3.connect('test.db')
>>> db.execute('create table t (a, b, c)')
>>> db.execute('insert into t values (1, 2, 3)')
>>> db.execute('select * from t').fetchall()
[(1, 2, 3)]
```
* **In this example values are not actually saved because `'db.commit()'` was omitted.**
### MySQL
**Has a very similar interface, with differences listed below.**
```python

28
index.html
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@ -1567,12 +1567,6 @@ db.close()
<ul>
<li><strong>New database will be created if path doesn't exist.</strong></li>
</ul>
<div><h3 id="create">Create</h3><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>db.execute(<span class="hljs-string">'create table t (a, b, c)'</span>)
<span class="hljs-meta">&gt;&gt;&gt; </span>db.execute(<span class="hljs-string">'insert into t values (1, 2, 3)'</span>)
<span class="hljs-meta">&gt;&gt;&gt; </span>db.execute(<span class="hljs-string">'select * from t'</span>).fetchall()
[(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>)]
</code></pre></div>
<div><h3 id="read">Read</h3><pre><code class="python language-python hljs">cursor = db.execute(<span class="hljs-string">'&lt;query&gt;'</span>)
<span class="hljs-keyword">if</span> cursor:
&lt;tuple&gt; = cursor.fetchone() <span class="hljs-comment"># First row.</span>
@ -1586,6 +1580,10 @@ db.close()
db.commit()
</code></pre></div>
<div><h4 id="or">Or:</h4><pre><code class="python language-python hljs"><span class="hljs-keyword">with</span> db:
db.execute(<span class="hljs-string">'&lt;query&gt;'</span>)
</code></pre></div>
<div><h3 id="placeholders">Placeholders</h3><pre><code class="python language-python hljs">db.execute(<span class="hljs-string">'&lt;query&gt;'</span>, &lt;list/tuple&gt;) <span class="hljs-comment"># Replaces '?'s in query with values.</span>
db.execute(<span class="hljs-string">'&lt;query&gt;'</span>, &lt;dict/namedtuple&gt;) <span class="hljs-comment"># Replaces ':&lt;key&gt;'s with values.</span>
db.executemany(<span class="hljs-string">'&lt;query&gt;'</span>, &lt;coll_of_above&gt;) <span class="hljs-comment"># Runs execute() many times.</span>
@ -1594,6 +1592,16 @@ db.executemany(<span class="hljs-string">'&lt;query&gt;'</span>, &lt;coll_of_abo
<ul>
<li><strong>Passed values can be of type str, int, float, bytes, None, bool, datetime.date or datetime.datetme.</strong></li>
</ul>
<div><h3 id="example">Example</h3><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>db = sqlite3.connect(<span class="hljs-string">'test.db'</span>)
<span class="hljs-meta">&gt;&gt;&gt; </span>db.execute(<span class="hljs-string">'create table t (a, b, c)'</span>)
<span class="hljs-meta">&gt;&gt;&gt; </span>db.execute(<span class="hljs-string">'insert into t values (1, 2, 3)'</span>)
<span class="hljs-meta">&gt;&gt;&gt; </span>db.execute(<span class="hljs-string">'select * from t'</span>).fetchall()
[(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>)]
</code></pre></div>
<ul>
<li><strong>In this example values are not actually saved because <code class="python hljs"><span class="hljs-string">'db.commit()'</span></code> was omitted.</strong> </li>
</ul>
<div><h3 id="mysql">MySQL</h3><p><strong>Has a very similar interface, with differences listed below.</strong></p><pre><code class="python language-python hljs"><span class="hljs-comment"># $ pip3 install mysql-connector</span>
<span class="hljs-keyword">from</span> mysql <span class="hljs-keyword">import</span> connector
db = connector.connect(host=&lt;str&gt;, user=&lt;str&gt;, password=&lt;str&gt;, database=&lt;str&gt;)
@ -1643,7 +1651,7 @@ cursor.execute(<span class="hljs-string">'&lt;query&gt;'</span>, &lt;dict/namedt
</code></pre></div>
<div><h3 id="example">Example</h3><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>pack(<span class="hljs-string">'&gt;hhl'</span>, <span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>)
<div><h3 id="example-1">Example</h3><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>pack(<span class="hljs-string">'&gt;hhl'</span>, <span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>)
<span class="hljs-string">b'\x00\x01\x00\x02\x00\x00\x00\x03'</span>
<span class="hljs-meta">&gt;&gt;&gt; </span>unpack(<span class="hljs-string">'&gt;hhl'</span>, <span class="hljs-string">b'\x00\x01\x00\x02\x00\x00\x00\x03'</span>)
(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>)
@ -1715,7 +1723,7 @@ lock.acquire()
lock.release()
</code></pre></div>
<div><h4 id="or">Or:</h4><pre><code class="python language-python hljs">lock = RLock()
<div><h4 id="or-1">Or:</h4><pre><code class="python language-python hljs">lock = RLock()
<span class="hljs-keyword">with</span> lock:
...
</code></pre></div>
@ -1754,7 +1762,7 @@ param_names = list(&lt;sig&gt;.parameters.keys())
</code></pre></div>
<div><h4 id="or-1">Or:</h4><pre><code class="python language-python hljs"><span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">MyMetaClass</span><span class="hljs-params">(type)</span>:</span>
<div><h4 id="or-2">Or:</h4><pre><code class="python language-python hljs"><span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">MyMetaClass</span><span class="hljs-params">(type)</span>:</span>
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__new__</span><span class="hljs-params">(cls, name, parents, attrs)</span>:</span>
attrs[<span class="hljs-string">'a'</span>] = <span class="hljs-string">'abcde'</span>
<span class="hljs-keyword">return</span> type.__new__(cls, name, parents, attrs)
@ -2097,7 +2105,7 @@ right = [[<span class="hljs-number">0.1</span> , <span class="hljs-number">0.6<
right = [[<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>], [<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>], [<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>]] <span class="hljs-comment"># Shape: (3, 3) &lt;- !</span>
</code></pre></div>
<div><h4 id="3ifneithernonmatchingdimensionhassize1riseanerror">3. If neither non-matching dimension has size 1, rise an error.</h4><div><h3 id="example-1">Example</h3><div><h4 id="foreachpointreturnsindexofitsnearestpoint010608121">For each point returns index of its nearest point (<code class="python hljs">[<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>] =&gt; [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">1</span>]</code>):</h4><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>points = np.array([<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>])
<div><h4 id="3ifneithernonmatchingdimensionhassize1riseanerror">3. If neither non-matching dimension has size 1, rise an error.</h4><div><h3 id="example-2">Example</h3><div><h4 id="foreachpointreturnsindexofitsnearestpoint010608121">For each point returns index of its nearest point (<code class="python hljs">[<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>] =&gt; [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">1</span>]</code>):</h4><pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>points = np.array([<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>])
[ <span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>wrapped_points = points.reshape(<span class="hljs-number">3</span>, <span class="hljs-number">1</span>)
[[ <span class="hljs-number">0.1</span>],

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