richard
/
python-cheatsheet
mirror of https://github.com/gto76/python-cheatsheet.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity
Browse Source

SQLite

pull/46/head
Jure Šorn 5 years ago
parent
a4747b54c0
commit
bd3cfe57c9
2 changed files with 29 additions and 31 deletions
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. 21
      README.md
  2. 39
      index.html

21
README.md
View File

@ -1456,14 +1456,13 @@ pprint(<collection>, width=80, depth=None)
Input
-----
* **Reads a line from user input or pipe if present.**
* **Trailing newline gets stripped.**
* **Prompt string is printed to the standard output before reading input.**
* **Raises EOFError when user hits EOF or input stream gets exhausted.**
**Reads a line from user input or pipe if present.**
```python
<str> = input(prompt=None)
```
* **Trailing newline gets stripped.**
* **Prompt string is printed to the standard output before reading input.**
* **Raises EOFError when user hits EOF or input stream gets exhausted.**
Command Line Arguments
@ -1795,6 +1794,8 @@ def write_to_csv_file(filename, rows):
SQLite
------
**Server-less database engine that stores each database into separate file.**
### Connect
```python
import sqlite3
db = sqlite3.connect('<path>') # Also ':memory:'.
@ -1804,12 +1805,12 @@ db.close()
* **New database will be created if path doesn't exist.**
### Read
**Returned values can be of type str, int, float, bytes or None.**
```python
<cursor> = db.execute('<query>') # Can raise sqlite3.OperationalError.
<tuple> = <cursor>.fetchone() # Returns next row. Also next(<cursor>).
<list> = <cursor>.fetchall() # Returns remaining rows.
```
* **Returned values can be of type str, int, float, bytes or None.**
### Write
```python
@ -1824,23 +1825,23 @@ with db:
```
### Placeholders
* **Passed values can be of type str, int, float, bytes, None, bool, datetime.date or datetime.datetme.**
* **Bools will be stored and returned as ints and dates as [ISO formatted strings](#encode).**
```python
db.execute('<query>', <list/tuple>) # Replaces '?'s in query with values.
db.execute('<query>', <dict/namedtuple>) # Replaces ':<key>'s with values.
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.**
* **Bools will be stored and returned as ints and dates as [ISO formatted strings](#encode).**
### Example
**In this example values are not actually saved because `'db.commit()'` is omitted!**
```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.**

39
index.html
View File

@ -1351,15 +1351,15 @@ pprint(&lt;collection&gt;, width=<span class="hljs-number">80</span>, depth=<spa
<ul>
<li><strong>Levels deeper than 'depth' get replaced by '…'.</strong></li>
</ul>
<div><h2 id="input"><a href="#input" name="input">#</a>Input</h2><ul>
<li><strong>Reads a line from user input or pipe if present.</strong></li>
<li><strong>Trailing newline gets stripped.</strong></li>
<li><strong>Prompt string is printed to the standard output before reading input.</strong></li>
<li><strong>Raises EOFError when user hits EOF or input stream gets exhausted.</strong></li>
</ul><pre><code class="python language-python hljs">&lt;str&gt; = input(prompt=<span class="hljs-keyword">None</span>)
<div><h2 id="input"><a href="#input" name="input">#</a>Input</h2><p><strong>Reads a line from user input or pipe if present.</strong></p><pre><code class="python language-python hljs">&lt;str&gt; = input(prompt=<span class="hljs-keyword">None</span>)
</code></pre></div>
<ul>
<li><strong>Trailing newline gets stripped.</strong></li>
<li><strong>Prompt string is printed to the standard output before reading input.</strong></li>
<li><strong>Raises EOFError when user hits EOF or input stream gets exhausted.</strong></li>
</ul>
<div><h2 id="commandlinearguments"><a href="#commandlinearguments" name="commandlinearguments">#</a>Command Line Arguments</h2><pre><code class="python language-python hljs"><span class="hljs-keyword">import</span> sys
script_name = sys.argv[<span class="hljs-number">0</span>]
arguments = sys.argv[<span class="hljs-number">1</span>:]
@ -1603,24 +1603,23 @@ shutil.copytree(from, to) <span class="hljs-comment"># Copies the entir
writer.writerows(rows)
</code></pre></div>
<div><h2 id="sqlite"><a href="#sqlite" name="sqlite">#</a>SQLite</h2><p><strong>Server-less database engine that stores each database into separate file.</strong></p><pre><code class="python language-python hljs"><span class="hljs-keyword">import</span> sqlite3
<div><h2 id="sqlite"><a href="#sqlite" name="sqlite">#</a>SQLite</h2><p><strong>Server-less database engine that stores each database into separate file.</strong></p><div><h3 id="connect">Connect</h3><pre><code class="python language-python hljs"><span class="hljs-keyword">import</span> sqlite3
db = sqlite3.connect(<span class="hljs-string">'&lt;path&gt;'</span>) <span class="hljs-comment"># Also ':memory:'.</span>
...
db.close()
</code></pre></div>
</code></pre></div></div>
<ul>
<li><strong>New database will be created if path doesn't exist.</strong></li>
</ul>
<div><h3 id="read-1">Read</h3><pre><code class="python language-python hljs">&lt;cursor&gt; = db.execute(<span class="hljs-string">'&lt;query&gt;'</span>) <span class="hljs-comment"># Can raise sqlite3.OperationalError.</span>
<div><h3 id="read-1">Read</h3><p><strong>Returned values can be of type str, int, float, bytes or None.</strong></p><pre><code class="python language-python hljs">&lt;cursor&gt; = db.execute(<span class="hljs-string">'&lt;query&gt;'</span>) <span class="hljs-comment"># Can raise sqlite3.OperationalError.</span>
&lt;tuple&gt; = &lt;cursor&gt;.fetchone() <span class="hljs-comment"># Returns next row. Also next(&lt;cursor&gt;).</span>
&lt;list&gt; = &lt;cursor&gt;.fetchall() <span class="hljs-comment"># Returns remaining rows.</span>
</code></pre></div>
<ul>
<li><strong>Returned values can be of type str, int, float, bytes or None.</strong></li>
</ul>
<div><h3 id="write-1">Write</h3><pre><code class="python language-python hljs">db.execute(<span class="hljs-string">'&lt;query&gt;'</span>)
db.commit()
</code></pre></div>
@ -1629,25 +1628,23 @@ db.commit()
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>
<div><h3 id="placeholders">Placeholders</h3><ul>
<li><strong>Passed values can be of type str, int, float, bytes, None, bool, datetime.date or datetime.datetme.</strong></li>
<li><strong>Bools will be stored and returned as ints and dates as <a href="#encode">ISO formatted strings</a>.</strong></li>
</ul><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>
</code></pre></div>
<ul>
<li><strong>Passed values can be of type str, int, float, bytes, None, bool, datetime.date or datetime.datetme.</strong></li>
<li><strong>Bools will be stored and returned as ints and dates as <a href="#encode">ISO formatted strings</a>.</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>)
<div><h3 id="example">Example</h3><p><strong>In this example values are not actually saved because <code class="python hljs"><span class="hljs-string">'db.commit()'</span></code> is omitted!</strong></p><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;)

Write Preview
Loading…
Cancel
Save