1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<title>pattern-db</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link type="text/css" rel="stylesheet" href="../clips.css" />
<style>
/* Small fixes because we omit the online layout.css. */
h3 { line-height: 1.3em; }
#page { margin-left: auto; margin-right: auto; }
#header, #header-inner { height: 175px; }
#header { border-bottom: 1px solid #C6D4DD; }
table { border-collapse: collapse; }
#checksum { display: none; }
</style>
<link href="../js/shCore.css" rel="stylesheet" type="text/css" />
<link href="../js/shThemeDefault.css" rel="stylesheet" type="text/css" />
<script language="javascript" src="../js/shCore.js"></script>
<script language="javascript" src="../js/shBrushXml.js"></script>
<script language="javascript" src="../js/shBrushJScript.js"></script>
<script language="javascript" src="../js/shBrushPython.js"></script>
</head>
<body class="node-type-page one-sidebar sidebar-right section-pages">
<div id="page">
<div id="page-inner">
<div id="header"><div id="header-inner"></div></div>
<div id="content">
<div id="content-inner">
<div class="node node-type-page"
<div class="node-inner">
<div class="breadcrumb">View online at: <a href="http://www.clips.ua.ac.be/pages/pattern-db" class="noexternal" target="_blank">http://www.clips.ua.ac.be/pages/pattern-db</a></div>
<h1>pattern.db</h1>
<!-- Parsed from the online documentation. -->
<div id="node-1432" class="node node-type-page"><div class="node-inner">
<div class="content">
<p class="big">The pattern.db module contains wrappers for databases (SQLite, MySQL), Unicode CSV files and Python's datetime. It offers a convenient way to work with tabular data, for example retrieved with the pattern.web module.</p>
<p>It can be used by itself or with other <a href="pattern.html">pattern</a> modules: <a href="pattern-web.html">web</a> | db | <a href="pattern-en.html">en</a> | <a href="pattern-search.html">search</a> <span class="blue"></span> | <a href="pattern-vector.html">vector</a> | <a href="pattern-graph.html">graph</a>.</p>
<p><img src="../g/pattern_schema.gif" alt="" width="620" height="180" /></p>
<hr />
<h2>Documentation</h2>
<ul style="margin-top: 0;">
<li><a href="#database">Database</a> <span class="smallcaps link-maintenance">(sqlite + mysql)</span></li>
<li><a href="#table">Table</a></li>
<li><a href="#query">Query</a></li>
<li><a href="#datasheet">Datasheet</a> <span class="smallcaps link-maintenance">(<a href="#csv">csv</a>)</span></li>
<li><a href="#date">Date</a></li>
</ul>
<p> </p>
<hr />
<h2><a name="database"></a>Database</h2>
<p>A database is a collection of tables. A table has rows of data with a specific data type (e.g., string, float) for each field or column. A database engine provides an interface to the database, using <a href="https://en.wikipedia.org/wiki/SQL" target="_blank">SQL</a> statements (Structured Query Language). Python 2.5+ comes bundled with the SQLite engine. The <a href="http://www.mysql.com/" target="_blank">MySQL</a> engine requires the <a href="http://sourceforge.net/projects/mysql-python/" target="_blank">MySQL-Python</a> bindings. Note that a 32-bit Python requires a 32-bit MySQL.</p>
<p>The <span class="inline_code">Database()</span> constructor creates (if necessary) and returns an <span class="inline_code">SQLITE</span> or <span class="inline_code">MYSQL</span> database. With <span class="inline_code">SQLITE</span>, it will create a file with the given name in the current folder.</p>
<pre class="brush:python; gutter:false; light:true;">db = Database(
name,
host = 'localhost',
port = 3306,
username = 'root',
password = '',
type = SQLITE
)
</pre><pre class="brush:python; gutter:false; light:true;">db.type # SQLITE | MYSQL
db.name # Database name.
db.host # Database host (MySQL).
db.port # Database port (MySQL).
db.username # Database username (MySQL).
db.password # Database password (MySQL).
db.tables # Dictionary of (name, Table)-items.
db.relations # List of relations, see Database.link().
db.query # Last executed SQL query.
db.connected # True after Database.connect(). </pre><pre class="brush:python; gutter:false; light:true;">db.connect() # Happens automatically.
db.disconnect()</pre><pre class="brush:python; gutter:false; light:true;">db.create(table, fields=[])
db.remove(table)
db.link(table1, field1, table2, field2, join=LEFT) </pre><pre class="brush:python; gutter:false; light:true;">db.execute(SQL, commit=False)
db.commit()
db.escape(value) # "a cat's tail" => "'a cat\'s tail'"</pre><ul>
<li><span class="inline_code">Database.execute()</span> returns an iterator of rows for the given SQL query.</li>
<li><span class="inline_code">Database.commit()</span> commits the changes of pending <span class="inline_code">INSERT</span>, <span class="inline_code">UPDATE</span>, <span class="inline_code">DELETE</span> queries.</li>
<li><span class="inline_code">Database.escape()</span> safely quotes and escapes field values.</li>
</ul>
<h3>Create table</h3>
<p><span class="inline_code">Database.create()</span> creates a new table in the database, It takes a table name and a list of row fields, where each field is defined with the <span class="inline_code">field()</span> function. Each field has a <span class="inline_code">name</span> (a-z + underscores) and a <span class="inline_code">type</span>, with an optional <span class="inline_code">default</span> value for new rows. The <span class="inline_code">pk()</span> function can be used for primary keys.</p>
<pre class="brush:python; gutter:false; light:true;">field(name, type=STRING, default=None, index=False, optional=True)</pre><pre class="brush: python;gutter: false; light: true; fontsize: 100; first-line: 1; ">pk(name='id') # field('id', INTEGER, index=PRIMARY, optional=False) </pre><table class="border">
<tbody>
<tr>
<td><span class="smallcaps">Type</span></td>
<td><span class="smallcaps">Value</span></td>
<td><span class="smallcaps">Example</span></td>
</tr>
<tr>
<td><span class="inline_code">STRING</span></td>
<td><span class="inline_code">str</span>, <span class="inline_code">unicode</span> (1-255 characters)</td>
<td><span class="inline_code">u'Schrödinger'</span></td>
</tr>
<tr>
<td><span class="inline_code">INTEGER</span></td>
<td><span class="inline_code">int</span></td>
<td><span class="inline_code">42</span></td>
</tr>
<tr>
<td><span class="inline_code">FLOAT</span></td>
<td><span class="inline_code">float</span></td>
<td><span class="inline_code">3.14159</span></td>
</tr>
<tr>
<td><span class="inline_code">TEXT</span></td>
<td><span class="inline_code">str</span>, <span class="inline_code">unicode</span></td>
<td><span class="inline_code">open('file.txt').read() </span></td>
</tr>
<tr>
<td><span class="inline_code">BLOB</span></td>
<td><span class="inline_code">str</span> (binary, e.g., PDF, PNG)</td>
<td><span class="inline_code">db.binary(open('img.jpg',</span> <span class="inline_code">'rb').read())</span></td>
</tr>
<tr>
<td><span class="inline_code">BOOLEAN</span></td>
<td><span class="inline_code">bool</span></td>
<td><span class="inline_code">True</span>, <span class="inline_code">False</span></td>
</tr>
<tr>
<td><span class="inline_code">DATE</span></td>
<td><span class="inline_code">Date</span></td>
<td><span class="inline_code">date('1999-12-31 23:59:59')</span></td>
</tr>
</tbody>
</table>
<p>A <span class="inline_code">STRING</span> field can contain up to a 100 characters. The length (1-255) can be changed by calling <span class="inline_code">STRING</span> as a function, e.g., <span class="inline_code">type=STRING(255)</span>. For longer strings, use <span class="inline_code">TEXT</span>. The default value for a <span class="inline_code">DATE</span> field is <span class="inline_code">NOW</span>.</p>
<p>With <span class="inline_code">index=True</span>, the field is indexed for faster search. The index can also be set to <span class="inline_code">UNIQUE</span> (no duplicates) or <span class="inline_code">PRIMARY</span>. A table must have a primary key field that uniquely identifies each row (i.e., an id). Integer primary keys are auto-numbered, there is no need to set the value manually in new rows.</p>
<p>With <span class="inline_code">optional=True</span>, the field is allowed to contain <span class="inline_code">None</span>.</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> from pattern.db import Database, field, pk, STRING, BOOLEAN, DATE, NOW
>>>
>>> db = Database('my_stuff')
>>> db.create('pets', fields=(
>>> pk(),
>>> field('name', STRING(80), index=True),
>>> field('type', STRING(20)),
>>> field('tail', BOOLEAN),
>>> field('date_birth', DATE, default=None),
>>> field('date_created', DATE, default=NOW)
>>> ))</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.append(name=u'Schrödinger', type='cat', tail=True)
>>> print db.pets.rows()[0]
(1, u'Schrödinger', u'cat', True, None, Date('2013-12-11 10:09:08'))</pre></div>
<h3>Create table from XML</h3>
<p><span class="inline_code">Database.create()</span> can also take a <span class="inline_code">Table.xml</span> or <span class="inline_code">Query.xml</span>. It creates a new table and copies the row data in the given XML string. An optional <span class="inline_code">name</span> parameter can be used to rename the new table. In <span class="inline_code">Query.xml</span>, a field name may contain a period. It will be replaced with an underscore (e.g., pets.name → pets_name). Alternatively, an alias can be defined in the <span class="inline_code">Query.aliases</span> dictionary.</p>
<p> </p>
<hr />
<h2><a name="table"></a>Table</h2>
<p>A <span class="inline_code">Table</span> is a list of rows, with one or more fields (i.e., table columns) of a certain type (i.e., string or number). A new table can be created with <span class="inline_code">Database.create()</span>. A <span class="inline_code">TableError</span> is raised if a table with the given name exists. An existing table can be retrieved with <span class="inline_code">Database.tables[name]</span>, <span class="inline_code">Database[name]</span> or <span class="inline_code">Database.<name></span>.</p>
<pre class="brush:python; gutter:false; light:true;">table = Database.tables[name]</pre><pre class="brush:python; gutter:false; light:true;">table.db # Parent Database.
table.name # Table name (a-z + underscores).
table.fields # List of field names (i.e., columns).
table.schema # Dictionary of (field, Schema)-items.
table.default # Dictionary of (field, value)-items for new rows.
table.pk # Primary key field name.</pre><pre class="brush:python; gutter:false; light:true;">table.count() # Total number of rows (len(table) also works).
table.rows() # List of rows, each a tuple of fields.
</pre><pre class="brush:python; gutter:false; light:true;">table.record(row) # Dictionary of (field, value)-items for given row.</pre><pre class="brush:python; gutter:false; light:true;">table.append(fields={}, commit=True)
table.update(id, fields={}, commit=True)
table.remove(id, commit=True)
</pre><pre class="brush:python; gutter:false; light:true;">table.filter(*args, **kwargs)
table.search(*args, **kwargs) </pre><pre class="brush:python; gutter:false; light:true;">table.xml # XML string with the table schema and rows.
table.datasheet # Datasheet object (see below).</pre><ul>
<li><span class="inline_code">Table.rows()</span> returns a list of all rows. To iterate rows memory-efficiently, use <span class="inline_code">iter(</span><span class="inline_code">Table)</span>.</li>
<li><span class="inline_code">Table.append()</span>, <span class="inline_code">update()</span> and <span class="inline_code">remove()</span> modify the table contents.<br />With <span class="inline_code">commit=False</span>, changes are only committed after <span class="inline_code">Database.commit()</span> (= faster in batch).</li>
<li><span class="inline_code">Table.filter()</span> returns a subset of rows with a subset of fields.<br />For example: <span class="inline_code">table.filter('name',</span> <span class="inline_code">type='cat')</span>.</li>
</ul>
<h3>Table schema</h3>
<p>The <span class="inline_code">Table.schema</span> dictionary contains field name → <span class="inline_code">Schema</span> items.</p>
<pre class="brush:python; gutter:false; light:true;">schema = Table.schema[fieldname]</pre><pre class="brush:python; gutter:false; light:true;">schema.name # Field name.
schema.type # STRING, INTEGER, FLOAT, TEXT, BLOB, BOOLEAN, DATE
schema.length # STRING field length.
schema.default # Default value.
schema.index # PRIMARY | UNIQUE | True | False
schema.optional # True or False. </pre><div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> from pattern.db import Database
>>>
>>> db = Database('my_stuff')
>>>
>>> print db.pets.fields
>>> print db.pets.schema['name'].type
>>> print db.pets.schema['name'].length
['id', 'name', 'tail', 'date_birth', 'date_created']
STRING
80 </pre></div>
<h3>Append row</h3>
<p><span class="inline_code">Table.append()</span> adds a new row with the given field values. It returns the row id, if the table has a primary key generated with <span class="inline_code">pk()</span>. Field values can be given as optional parameters, a dictionary or a tuple. Field values for a <span class="inline_code">BLOB</span> field must be wrapped in <span class="inline_code">Database.binary()</span>.<span style="color: #333333; font-family: Inconsolata, 'Courier New', Courier, monospace; font-size: small;"></span></p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.append(name=u'Schrödinger', date_birth=date('2009-08-12'))</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.append({'name': u'Schrödinger', 'date_birth': date('2009-08-12')}) </pre></div>
<div class="example">
<pre class="brush: python;gutter: false; light: true; fontsize: 100; first-line: 1; ">>>> db.pets.append((u'Schrödinger', 'cat', True, date('2009-08-12')) # in-order</pre></div>
<h3>Update row</h3>
<p><span class="inline_code">Table.update()</span> updates values in the row with the given primary key. A batch of rows can be updated using a <a class="link-maintenance" href="#filter">filter</a>, or a chain of filters with <span class="inline_code">any()</span> or <span class="inline_code">all()</span>. In the last example, all rows with <span class="inline_code">type='cat'</span> will have their <span class="inline_code">tail</span> field set to <span class="inline_code">True</span>.</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.update(1, type='cat') # set type='cat' in row with id=1.</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.update(1, {'type': 'cat'})</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.update(eq('type', 'cat'), tail=True) </pre></div>
<h3>Remove row</h3>
<p><span class="inline_code">Table.remove()</span> removes the row with the given primary key:</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.remove(1)</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.remove(ALL)</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.remove(all(eq('type', 'cat'), lt(year('date_birth'), 1990, '<')))</pre></div>
<p>The last example removes all rows that have <span class="inline_code">type='cat'</span> AND year of birth before 1990.</p>
<h3><span>Filter rows</span></h3>
<p><span class="inline_code">Table.filter()</span> returns a list of rows filtered by field value(s), where each row is a tuple of fields. The first parameter defines which fields to return. It can be a single field name, a list of field names or <span class="inline_code">ALL</span>. The following parameters are optional and define field constraints. They can also be given as a dictionary:</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.filter('name') # all rows, name</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.filter(('id', 'name')) # all rows, name + id</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.filter(ALL, type='cat') # type='cat', all fields</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.filter(ALL, type=('cat', 'dog')) # type='cat' OR type='dog' </pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.filter(ALL, type='*at') # type='cat' OR 'hat' OR 'brat', ...</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.filter(ALL, type='cat', tail=True) # type='cat' AND tail=True </pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.pets.filter('id', {'type': 'cat', 'tail': True})
</pre></div>
<p>More complex queries can be constructed with a <span class="inline_code">Query</span>.</p>
<p> </p>
<hr />
<h2><a name="query"></a>Query</h2>
<p><span class="inline_code">Table.search()</span> returns a new <span class="inline_code">Query</span> with options for filtering, sorting and ordering rows by field value(s). It can include fields from other, related tables.</p>
<pre class="brush:python; gutter:false; light:true;">query = Table.search(
fields = ALL,
filters = [],
relations = [],
sort = None,
order = ASCENDING,
group = None,
function = FIRST,
range = None
)</pre><pre class="brush:python; gutter:false; light:true;">query.table # Parent Table.
query.fields # Field name, list of field names, or ALL.
query.aliases # Dictionary of (field name, alias)-items.
query.filters # List of filter() objects.
query.relations # List of rel() objects.
query.sort # Field name or list of field names.
query.order # ASCENDING | DESCENDING
query.group # Field name or list of field names.
query.function # FIRST, LAST, COUNT, MIN, MAX, SUM, AVG, CONCATENATE
query.range # (start, stop)-tuple, e.g. rows 11-20.</pre><pre class="brush:python; gutter:false; light:true;">query.sql() # SQL string, can be used with Database.execute().</pre><pre class="brush:python; gutter:false; light:true;">query.rows() # List of rows, each a tuple of fields.</pre><pre class="brush:python; gutter:false; light:true;">query.record(row) # Dictionary of (field, value)-items for given row.</pre><pre class="brush:python; gutter:false; light:true;">query.xml # XML string with the query schema and rows.</pre><p>To iterate rows memory-efficiently, use <span class="inline_code">iter(Query)</span> instead of <span class="inline_code">Query.rows()</span>.</p>
<h3><a name="filter"></a>Query filter</h3>
<p>The <span class="inline_code">filter()</span> function creates a field-value constraint that matches certain rows in a table. A list of filters can be passed to the <span class="inline_code">filters</span> parameter of a <span class="inline_code">Query</span>.</p>
<pre class="brush:python; gutter:false; light:true;">filter(field, value, comparison='=')</pre><table class="border">
<tbody>
<tr>
<td style="text-align: center;"><span class="smallcaps">Comparison</span></td>
<td><span class="smallcaps">Description</span></td>
<td><span class="smallcaps">Example</span></td>
<td style="text-align: center;"><span class="smallcaps">Alias</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="inline_code">=</span></td>
<td>equal to</td>
<td><span class="inline_code">filter('type',</span> <span class="inline_code">('cat',</span> <span class="inline_code">'dog'),</span> <span class="inline_code">'=') </span></td>
<td style="text-align: left;"><span class="inline_code"> eq()</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="inline_code">i=</span></td>
<td>equal to (case-insensitive)</td>
<td><span class="inline_code">filter('name',</span> <span class="inline_code">'tig*',</span> <span class="inline_code">'i=') </span></td>
<td style="text-align: left;"><span class="inline_code"> eqi()</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="inline_code">!=</span></td>
<td>not equal to</td>
<td><span class="inline_code">filter('name',</span> <span class="inline_code">'*y',</span> <span class="inline_code">'!=')</span></td>
<td style="text-align: left;"><span class="inline_code"> ne()</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="inline_code">></span></td>
<td>greater than</td>
<td><span class="inline_code">filter('weight',</span> <span class="inline_code">10,</span> <span class="inline_code">'>') </span></td>
<td style="text-align: left;"><span class="inline_code"> gt()</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="inline_code"><</span></td>
<td>less than</td>
<td><span class="inline_code">filter('weight',</span> <span class="inline_code">10,</span> <span class="inline_code">'<') </span></td>
<td style="text-align: left;"><span class="inline_code"> lt()</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="inline_code">>=</span></td>
<td>greater than or equal to</td>
<td><span class="inline_code">filter(year('date'),</span> <span class="inline_code">1999,</span> <span class="inline_code">'>=') </span></td>
<td style="text-align: left;"><span class="inline_code"> gte()</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="inline_code"><=</span></td>
<td>less than or equal to</td>
<td><span class="inline_code">filter(year('date'),</span> <span class="inline_code">2002,</span> <span class="inline_code">'<=')</span></td>
<td style="text-align: left;"><span class="inline_code"> lte()</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="inline_code">:</span></td>
<td>between (inclusive)</td>
<td><span class="inline_code">filter(year('date'),</span> <span class="inline_code">(1999,</span> <span class="inline_code">2002),</span> <span class="inline_code">':')</span></td>
<td style="text-align: left;"><span class="inline_code"> rng()</span></td>
</tr>
</tbody>
</table>
<p>The field name of a <span class="inline_code">DATE</span> field can be passed to the <span class="inline_code">year()</span>, <span class="inline_code">month()</span>, <span class="inline_code">day()</span>, <span class="inline_code">hour()</span>, <span class="inline_code">minute()</span> or <span class="inline_code">second()</span> function.The short aliases of <span class="inline_code">filter()</span> have a preset comparison operator.</p>
<h3>Query filter chain</h3>
<p>Filters can be chained together. The <span class="inline_code">all()</span> function returns a list with AND logic. The <span class="inline_code">any()</span> function returns a list with OR logic. In the example below, the first query matches <span style="text-decoration: underline;">all</span> cats named Taxi. The second and third query match <span style="text-decoration: underline;">any</span> pet that is cat OR that is named Taxi.</p>
<pre class="brush:python; gutter:false; light:true;">all(filter1, filter2, ...) # Rows must match ALL of the filters.</pre><pre class="brush:python; gutter:false; light:true;">any(filter1, filter2, ...) # Rows must match ANY of the filters.</pre><div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> from pattern.db import Database, eq, all, any
>>>
>>> db = Database('my_stuff')
>>>
>>> db.pets.search(filters=all(eq('name', 'Taxi'), eq('type', 'cat')))
>>> db.pets.search(filters=any(eq('name', 'Taxi'), eq('type', 'cat')))
>>> db.pets.search(filters=any(name='Taxi', type='cat')) </pre></div>
<p>Lists created with <span class="inline_code">all()</span> and <span class="inline_code">any()</span> can be nested to define complex search criteria. The example below matches all pets that are cats, and whose name starts with Fluff- OR ends with a -y:</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> f = any(eq('name', 'Fluff*'), eq('name', '*y')) # OR
>>> f = all(eq('type', 'cat'), f) # AND
>>>
>>> for row in db.pets.search(filters=f):
>>> print row</pre></div>
<p>The syntax can even be more concise:</p>
<div class="example">
<pre class="brush: python;gutter: false; light: true; fontsize: 100; first-line: 1; ">>>> for row in db.pets.search(filters=all(name=('Fluff*', '*y'), type='cat')):
>>> print row </pre></div>
<h3>Query relation</h3>
<p>The <span class="inline_code">rel()</span> function defines a relation between two fields in different tables (usually id's).</p>
<pre class="brush: python;gutter: false; light: true; fontsize: 100; first-line: 1; ">rel(field1, field2, table, join=LEFT) # LEFT | INNER</pre><p>The optional <span class="inline_code">join</span> parameter defines how rows are matched. <span class="inline_code">LEFT</span> takes all rows from the base table, with additional fields from the related table. For a row with no match between <span class="inline_code">field1</span> and <span class="inline_code">field2</span>, these fields have value <span class="inline_code">None</span>. <span class="inline_code">INNER</span> takes the subset of rows that have a match between <span class="inline_code">field1</span> and <span class="inline_code">field2</span>.</p>
<p>A well-known example is a database app that processes invoices. Say we have a products table and an orders table. Each order has a product id – instead of all product details. Each product id can occur in multiple orders. This approach is called database normalization. It avoids duplicate data. To generate an invoice, we can combine product details and order details using a query relation.</p>
<p>The following example demonstrates a simple products + customers + orders database app:</p>
<table class="border=">
<tbody>
<tr>
<td>
<table class="border" style="margin: 0;">
<tbody>
<tr>
<td style="text-align: center;" colspan="3"><span class="smallcaps">products</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="smallcaps">id</span></td>
<td style="text-align: left;"><span class="smallcaps">name</span></td>
<td style="text-align: center;"><span class="smallcaps">price</span></td>
</tr>
<tr>
<td style="text-align: center;">1</td>
<td style="text-align: left;">pizza</td>
<td style="text-align: center;">15</td>
</tr>
<tr>
<td style="text-align: center;">2</td>
<td style="text-align: left;">garlic bread</td>
<td style="text-align: center;">3</td>
</tr>
</tbody>
</table>
</td>
<td>
<table class="border" style="margin: 0;">
<tbody>
<tr>
<td style="text-align: center;" colspan="3"><span class="smallcaps">customers</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="smallcaps">id</span></td>
<td style="text-align: left;"><span class="smallcaps">name</span></td>
</tr>
<tr>
<td style="text-align: center;">1</td>
<td style="text-align: left;">Schrödinger</td>
</tr>
<tr>
<td style="text-align: center;">2</td>
<td style="text-align: left;">Hofstadter</td>
</tr>
</tbody>
</table>
</td>
<td>
<table class="border" style="margin: 0;">
<tbody>
<tr>
<td style="text-align: center;" colspan="3"><span class="smallcaps">orders</span></td>
</tr>
<tr>
<td style="text-align: center;"><span class="smallcaps">id</span></td>
<td style="text-align: center;"><span class="smallcaps">product</span></td>
<td style="text-align: center;"><span class="smallcaps">customer</span></td>
</tr>
<tr>
<td style="text-align: center;">1</td>
<td style="text-align: center;">1</td>
<td style="text-align: center;">2</td>
</tr>
<tr>
<td> </td>
<td> </td>
<td> </td>
</tr>
</tbody>
</table>
</td>
</tr>
</tbody>
</table>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> from pattern.db import Database, field, pk, INTEGER as I
>>>
>>> db = Database('pizza_delivery')
>>>
>>> db.create( 'products', (pk(), field('name'), field('price', I)))
>>> db.create('customers', (pk(), field('name')))
>>> db.create( 'orders', (pk(), field('product', I), field('customer', I)))</pre></div>
<div class="example">Add products and customers. Pizza delivery is open for business!</div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.products.append(name='pizza', price=15)
>>> db.products.append(name='garlic bread', price=3)</pre></div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.customers.append(name=u'Schrödinger')
>>> db.customers.append(name=u'Hofstadter')</pre></div>
<p>Hofstadter orders a pizza.</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> db.orders.append(product=1, customer=2)</pre></div>
<div class="example">An orders query with relations to products and customers generates a human-readable invoice:</div>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> from pattern.db import Database, rel
>>>
>>> db = Database('pizza_delivery')
>>>
>>> f = ('orders.id', 'customers.name', 'products.name', 'products.price')
>>> q = db.orders.search(f, relations=(
>>> rel('orders.customer', 'customers.id', 'customers'),
>>> rel('orders.product', 'products.id', 'products'))
>>> )
>>> for row in q:
>>> print q.record(row)
{ 'orders.id' : 1,
'customers.name' : u'Hofstadter',
'products.name' : u'pizza',
'products.price' : 15 }</pre></div>
<div class="example">If a relation is used repeatedly, define it once with <span class="inline_code">Database.link()</span>. It will be available in every <span class="inline_code">Query</span>.</div>
<h3>Grouping rows</h3>
<p>A <span class="inline_code">Query</span> has an optional parameter <span class="inline_code">group</span> that can be used to merge rows on duplicate field values. The given <span class="inline_code">function</span> is applied to the other fields. It can also be a list with a function for each field.</p>
<table class="border">
<tbody>
<tr>
<td><span class="smallcaps">Function</span></td>
<td style="text-align: center;"><span class="smallcaps">Field type</span></td>
<td><span class="smallcaps">Description</span></td>
</tr>
<tr>
<td><span class="inline_code">FIRST</span></td>
<td style="text-align: center;">any</td>
<td>The first row field in the group.</td>
</tr>
<tr>
<td><span class="inline_code">LAST</span></td>
<td style="text-align: center;">any</td>
<td>The last row field in the group.</td>
</tr>
<tr>
<td><span class="inline_code">COUNT</span></td>
<td style="text-align: center;">any</td>
<td>The number of rows in the group.</td>
</tr>
<tr>
<td><span class="inline_code">MIN</span></td>
<td style="text-align: center;"><span class="inline_code">INTEGER</span> + <span class="inline_code">FLOAT</span></td>
<td>The lowest field value in the group.</td>
</tr>
<tr>
<td><span class="inline_code">MAX</span></td>
<td style="text-align: center;"><span class="inline_code">INTEGER</span> + <span class="inline_code">FLOAT</span></td>
<td>The highest field value in the group.</td>
</tr>
<tr>
<td><span class="inline_code">SUM</span></td>
<td style="text-align: center;"><span class="inline_code">INTEGER</span> + <span class="inline_code">FLOAT</span></td>
<td>The sum of all field values in the group.</td>
</tr>
<tr>
<td><span class="inline_code">AVG</span></td>
<td style="text-align: center;"><span class="inline_code">INTEGER</span> + <span class="inline_code">FLOAT</span></td>
<td>The average of all field values in the group.</td>
</tr>
<tr>
<td><span class="inline_code">STDEV</span></td>
<td style="text-align: center;"><span class="inline_code">INTEGER</span> + <span class="inline_code">FLOAT</span></td>
<td>The standard deviation (= variation from average).</td>
</tr>
<tr>
<td><span class="inline_code">CONCATENATE</span></td>
<td style="text-align: center;"><span class="inline_code">STRING</span></td>
<td>Joins all field values with a comma.</td>
</tr>
</tbody>
</table>
<p>For example, to get the total revenue per ordered product:</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> print db.orders.search(
>>> fields = ('products.name', 'products.price'),
>>> relations = rel('product', 'products.id', 'products'),
>>> group = 'products.name', # Merge orders with same product name.
>>> function = SUM # Sum of product prices.
>>> ).rows()</pre></div>
<p> </p>
<hr />
<h2><a name="datasheet"></a>Datasheet</h2>
<p>A <span class="inline_code">Datasheet</span> is a matrix of rows and columns, where each row and column can be retrieved as a list. The data can be imported or exported as a CSV-file. Optionally, the given <span class="inline_code">fields</span> is a list of <span class="inline_code">(name,</span> <span class="inline_code">type)</span> headers, where <span class="inline_code">type</span> can be <span class="inline_code">STRING</span>, <span class="inline_code">TEXT</span>, <span class="inline_code">INTEGER</span>, <span class="inline_code">FLOAT</span>, <span class="inline_code">BOOLEAN</span>, <span class="inline_code">BLOB</span> or <span class="inline_code">DATE</span>.</p>
<pre class="brush:python; gutter:false; light:true;">datasheet = Datasheet(rows=[], fields=None)</pre><pre class="brush:python; gutter:false; light:true;">datasheet = Datasheet.load(path, separator=',', decoder=lambda v: v, headers=False)
</pre><pre class="brush:python; gutter:false; light:true;">datasheet.rows # List of rows (each row = list of values).
datasheet.columns # List of columns (each column = list of values).
datasheet.fields # List of (name, type) column headers.
datasheet.<field> # List of column values. </pre><pre class="brush:python; gutter:false; light:true;">datasheet[i] # Row at index i.
datasheet[i, j] # Value in row i at column j.
datasheet[i1:i2, j] # Slice of column j from rows i1-i2.
datasheet[i, j1:j2] # Slice of columns j1-j2 from row i.
datasheet[i1:i2, j1:j2] # Datasheet with columns j1-j2 from rows i1-i2.
datasheet[:] # Datasheet copy. </pre><pre class="brush:python; gutter:false; light:true;">datasheet.insert(i, row, default=None)
datasheet.append(row, default=None)
datasheet.extend(rows, default=None)
datasheet.copy(rows=ALL, columns=ALL)</pre><pre class="brush:python; gutter:false; light:true;">datasheet.group(j, function=FIRST, key=lambda v: v)</pre><pre class="brush:python; gutter:false; light:true;">datasheet.save(path, separator=',', encoder=lambda v: v, headers=False)</pre><pre class="brush:python; gutter:false; light:true;">datasheet.json # JSON-formatted string.</pre><ul>
<li><span class="inline_code">Datasheet.insert()</span> and <span class="inline_code">append()</span> fill missing columns with the <span class="inline_code">default</span> value.</li>
<li><span class="inline_code">Datasheet.columns.insert()</span> and <span class="inline_code">append()</span> fill missing rows with the <span class="inline_code">default</span> value.<br />An optional <span class="inline_code">field</span> parameter can be used to supply a (<span class="inline_code">name</span>, <span class="inline_code">type</span>) column header.</li>
<li><span class="inline_code">Datasheet.copy()</span> returns a new <span class="inline_code">Datasheet</span> from a selective list of row and/or column indices.</li>
<li>To rotate a datasheet 90 degrees, use <span class="inline_code">datasheet</span> <span class="inline_code">=</span> <span class="inline_code">flip(datasheet)</span>.</li>
</ul>
<p>For example:</p>
<div class="example">
<pre class="brush: python;gutter: false; light: true; fontsize: 100; first-line: 1; ">>>> from pattern.db import Datasheet
>>>
>>> ds = Datasheet()
>>> ds.append((u'Schrödinger', 'cat'))
>>> ds.append((u'Hofstadter', 'cat'))
>>> ds.save('pets.csv')
>>>
>>> ds = Datasheet.load('pets.csv')
>>> print ds
[[u'Schrödinger', 'cat'],
[ u'Hofstadter', 'cat']]</pre></div>
<h3>Grouping rows</h3>
<p><span class="inline_code">Datasheet.group(j)</span> returns a new <span class="inline_code">Datasheet</span> with unique values in column <span class="inline_code">j</span>. It merges rows using a given <span class="inline_code">function</span> that takes a list of column values and returns a single value. Predefined functions are <span class="inline_code">FIRST</span>, <span class="inline_code">LAST</span>, <span class="inline_code">COUNT</span>, <span class="inline_code">MIN</span>, <span class="inline_code">MAX</span>, <span class="inline_code">SUM</span>, <span class="inline_code">AVG</span>, <span class="inline_code">STDEV</span> and <span class="inline_code">CONCATENATE</span>. It can also be a list of functions.</p>
<p>The optional <span class="inline_code">key</span> can be used to compare the values in column <span class="inline_code">j</span>. For example, <span class="inline_code">lambda</span> <span class="inline_code">date:</span> <span class="inline_code">date.year</span> groups a column of <span class="inline_code">Date</span> objects by year.</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> from pattern.db import Datasheet, pprint
>>>
>>> ds = Datasheet(rows=[
>>> (1, u'Schrödinger', 'cat'),
>>> (2, u'Hofstadter', 'cat'),
>>> (3, u'Taxi', 'dog')
>>> ])
>>>
>>> g = ds.copy(columns=[2, 0]) # A copy with type & id.
>>> g = g.group(0, COUNT) # Group type, count rows per type.
>>> pprint(g, fill='')
cat 2
dog 1 </pre></div>
<h3>Sorting rows & columns</h3>
<p><span class="inline_code">Datasheet.columns[j].sort()</span> sorts the rows according to the values in column <span class="inline_code">j</span>. <br /><span class="inline_code">Datasheet.columns.sort()</span> can be used to change the column order:</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> ds.columns.sort(order=[0, 2, 1])
>>> pprint(ds, fill='')
1 cat Schrödinger
2 cat Hofstadter
3 dog Taxi</pre></div>
<p><span class="inline_code">Datasheet.columns.swap(j1,j2)</span> swaps two individual columns with given indices.</p>
<h3><a name="csv"></a>CSV import & export</h3>
<p><span class="inline_code">Datasheet.save()</span> exports the matrix as a CSV file. <span class="inline_code">Datasheet.load()</span> returns a <span class="inline_code">Datasheet</span> from a given CSV file. CSV (comma-separated values) is a simple text format for tabular data, where each line is a row and each value is separated by a comma.</p>
<pre class="brush:python; gutter:false; light:true;">datasheet = Datasheet.load(path, separator=',', decoder=lambda v: v, headers=False)</pre><pre class="brush:python; gutter:false; light:true;">datasheet.save(path, separator=',', encoder=lambda v: v, headers=False)</pre><p>On export, all <span class="inline_code">str</span>, <span class="inline_code">int</span>, <span class="inline_code">float</span>, <span class="inline_code">bool</span> and <span class="inline_code">Date</span> values are converted to Unicode. An <span class="inline_code">encoder</span> can be given for other data types. On import, all values in the datasheet will be Unicode unless a <span class="inline_code">decoder</span> is given.</p>
<p>With <span class="inline_code">headers=True</span>, the <span class="inline_code">Datasheet.fields</span> headers are exported and imported (first line in CSV). In this case, the data type for each column (<span class="inline_code">STRING</span>, <span class="inline_code">INTEGER</span>, <span class="inline_code">FLOAT</span>, <span class="inline_code">BOOLEAN</span> or <span class="inline_code">DATE</span>) is explicitly known and no <span class="inline_code">encoder</span> or <span class="inline_code">decoder</span> is needed.</p>
<div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> from pattern.db import Datasheet, STRING, DATE, date
>>>
>>> ds = Datasheet(fields=(('name', STRING), ('date', DATE)))
>>> ds.append((u'Schrödinger', date('1887-08-12')))
>>> ds.append((u'Hofstadter', date('1945-02-15')))
>>>
>>> ds.save('pets.csv', headers=True)
>>>
>>> ds = Datasheet.load('pets.csv', headers=True)
>>> print ds[0]
[u'Schrödinger', Date('1887-08-12 00:00:00')]
</pre></div>
<p>The <span class="inline_code">csv()</span> function can also be used instead of <span class="inline_code">Datasheet.load()</span>:</p>
<div class="example">
<pre class="brush: python;gutter: false; light: true; fontsize: 100; first-line: 1; ">>>> from pattern.db import csv
>>>
>>> for name, date in csv('pets.csv', separator=',', headers=True):
>>> print name, date</pre></div>
<p> </p>
<hr />
<h2><a name="date"></a>Date</h2>
<p>The <span class="inline_code">date()</span> function returns a new <span class="inline_code">Date</span>, a convenient subclass of Python's <span class="inline_code">datetime.datetime</span>. It takes an integer (Unix timestamp), a string or <span class="inline_code">NOW</span>. An optional string input format and output format can be given (e.g., <span class="inline_code">"%d/%m/%y"</span>). The default output format is <span class="inline_code">"YYYY-MM-DD hh:mm:ss"</span>.</p>
<pre class="brush:python; gutter:false; light:true;">d = date(int)</pre><pre class="brush:python; gutter:false; light:true;">d = date(NOW, format=DEFAULT)
</pre><pre class="brush:python; gutter:false; light:true;">d = date(string)</pre><pre class="brush:python; gutter:false; light:true;">d = date(string, format=DEFAULT)</pre><pre class="brush:python; gutter:false; light:true;">d = date(string, inputformat, format=DEFAULT)</pre><pre class="brush:python; gutter:false; light:true;">d = date(year, month, day, format=DEFAULT)</pre><pre class="brush:python; gutter:false; light:true;">d = date(year, month, day, hours, minutes, seconds, format=DEFAULT)</pre><pre class="brush: python;gutter: false; light: true; fontsize: 100; first-line: 1; ">d.year
d.month # 1-12
d.week # 1-52
d.weekday # 1-7
d.day # 1-31
d.minute # 1-60
d.second # 1-60
d.timestamp # Seconds elapsed since 1/1/1970.</pre><p>If no string input format is given, a number of common formats will be tried:</p>
<table class="border">
<tbody>
<tr>
<td><span class="smallcaps">Format</span></td>
<td><span class="smallcaps">Example</span></td>
</tr>
<tr>
<td><span class="inline_code">%Y-%m-%d %H:%M:%S</span></td>
<td>2010-09-21 09:27:01</td>
</tr>
<tr>
<td><span class="inline_code">%a, %d %b %Y %H:%M:%S %z</span></td>
<td>Tue, 9 Sep 2010 17:58:28 +0000</td>
</tr>
<tr>
<td><span class="inline_code">%Y-%m-%dT%H:%M:%SZ</span></td>
<td>2010-09-20T09:27:01Z</td>
</tr>
<tr>
<td><span class="inline_code">%Y-%m-%dT%H:%M:%S+0000</span></td>
<td>2010-09-20T09:27:01+0000</td>
</tr>
<tr>
<td><span class="inline_code">%Y-%m-%d %H:%M</span></td>
<td>2010-09-20 09:27</td>
</tr>
<tr>
<td><span class="inline_code">%Y-%m-%d</span></td>
<td>2010-09-20</td>
</tr>
<tr>
<td><span class="inline_code">%d/%m/%Y</span></td>
<td>20/09/2010</td>
</tr>
<tr>
<td><span class="inline_code">%d %B %Y</span></td>
<td>9 september 2010</td>
</tr>
<tr>
<td><span class="inline_code">%B %d %Y</span></td>
<td>September 9 2010</td>
</tr>
<tr>
<td><span class="inline_code">%B %d, %Y</span></td>
<td>September 09, 2010</td>
</tr>
</tbody>
</table>
<p>All date formats used in <a class="link-maintenance" href="pattern-web.html">pattern.web</a> (e.g., Twitter search result) are automatically detected.<br />For an overview of date format syntax, see: <a href="http://docs.python.org/library/time.html#time.strftime" target="_blank">http://docs.python.org/library/time.html#time.strftime</a>.<br /> </p>
<p><span class="smallcaps">Date calculations</span></p>
<p>The <span class="inline_code">time()</span> function can be used to add or subtract time to a <span class="inline_code">Date</span>:</p>
<pre class="brush:python; gutter:false; light:true;">time(days=0, seconds=0, minutes=0, hours=0)</pre><div class="example">
<pre class="brush:python; gutter:false; light:true;">>>> from pattern.db import date, time
>>>
>>> d = date('23 august 2011')
>>> d += time(days=2, hours=5)
>>> print type(d)
>>> print d
>>> print d.year, d.month, d.day
<class 'pattern.db.Date'>
2011-08-25 05:00:00
2011, 8, 25 </pre></div>
<p> </p>
<hr />
<h2>See also</h2>
<ul>
<li><a href="http://www.cherrypy.org/" target="_blank">CherryPy</a> (BSD): o<span>bject-oriented HTTP framework for Python.</span></li>
<li><span><a href="https://www.djangoproject.com/" target="_blank">Django</a> (BSD): m</span><span>odel-view-controller framework for Python.</span></li>
</ul>
</div>
</div></div>
</div>
</div>
</div>
</div>
</div>
</div>
<script>
SyntaxHighlighter.all();
</script>
</body>
</html>
|
