Python中使用SQLAlchemy连接Mysql数据库2（多表连接操作）
mysql
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http://blog.csdn.net/u011573853/article/details/51355113 在上面我们已经说了单表的一些操作，现在我们说一下多表的连接 from sqlalchemy import distinct from sqlalchemy.orm import aliased Astu = aliased(Stu, 'Astu' ) Acla = aliased(Cla, 'Acla'
http://blog.csdn.net/u011573853/article/details/51355113
在上面我们已经说了单表的一些操作，现在我们说一下多表的连接
<code class=" hljs python"><span class="hljs-prompt">>>> </span><span class="hljs-keyword">from</span> sqlalchemy <span class="hljs-keyword">import</span> distinct <span class="hljs-prompt">>>> </span><span class="hljs-keyword">from</span> sqlalchemy.orm <span class="hljs-keyword">import</span> aliased <span class="hljs-prompt">>>> </span>Astu = aliased(Stu,<span class="hljs-string">'Astu'</span>) <span class="hljs-prompt">>>> </span>Acla = aliased(Cla,<span class="hljs-string">'Acla'</span>) <span class="hljs-prompt">>>> </span>Agrade = aliased(Grade,<span class="hljs-string">'Agrade'</span>)</code>
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在这里先用函数aliased（）给表起一个别名以备使用
<code class=" hljs r"><span class="hljs-comment">#查询所有有成绩的学号</span> >>> query = session.query(Stu).join(Grade,Stu.id==Grade.uid).all() SELECT stu.id AS stu_id, stu.name AS stu_name FROM stu INNER JOIN grade ON stu.id = grade.uid <span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">15</span>:<span class="hljs-number">02</span>:<span class="hljs-number">36</span>,<span class="hljs-number">476</span> INFO sqlalchemy.engine.base.Engine () >>> <span class="hljs-keyword">for</span> re <span class="hljs-keyword">in</span> query: <span class="hljs-keyword">...</span> print re.id <span class="hljs-keyword">...</span> <span class="hljs-number">1</span> <span class="hljs-number">2</span> <span class="hljs-number">3</span> <span class="hljs-number">4</span> <span class="hljs-number">5</span> >>> </code>
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<code class=" hljs cpp"><span class="hljs-preprocessor">#查找有成绩的同学的学号好成绩</span> >>> print session.query(Grade.uid,Grade.gre).join(Stu,Grade.uid==Stu.id).all() SELECT grade.uid AS grade_uid, grade.gre AS grade_gre FROM grade INNER JOIN stu ON grade.uid = stu.id <span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">15</span>:<span class="hljs-number">15</span>:<span class="hljs-number">22</span>,<span class="hljs-number">208</span> INFO sqlalchemy.engine.base.Engine () [(<span class="hljs-number">1L</span>, <span class="hljs-number">76L</span>), (<span class="hljs-number">1L</span>, <span class="hljs-number">76L</span>), (<span class="hljs-number">2L</span>, <span class="hljs-number">66L</span>), (<span class="hljs-number">2L</span>, <span class="hljs-number">76L</span>), (<span class="hljs-number">2L</span>, <span class="hljs-number">50L</span>), (<span class="hljs-number">3L</span>, <span class="hljs-number">96L</span>), (<span class="hljs-number">3L</span>, <span class="hljs-number">76L</span>), (<span class="hljs-number">3L</span>, <span class="hljs-number">60L</span>), (<span class="hljs-number">4L</span>, <span class="hljs-number">76L</span>), (<span class="hljs-number">4L</span>, <span class="hljs-number">76L</span>), (<span class="hljs-number">4L</span>, <span class="hljs-number">76L</span>), (<span class="hljs-number">5L</span>, <span class="hljs-number">66L</span>), (<span class="hljs-number">5L</span>, <span class="hljs-number">96L</span>), (<span class="hljs-number">5L</span>, <span class="hljs-number">96L</span>)] >>> </code>
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<code class=" hljs oxygene">#查找有成绩同学的学好成绩和课程名 >>>print session.query(Grade.uid,Grade.gre,Cla.cname).<span class="hljs-keyword">join</span>(Stu,Grade.uid==Stuid).<span class="hljs-keyword">join</span>(Cla,Grade.cid==Cla.id).all() <span class="hljs-keyword">SELECT</span> grade.uid <span class="hljs-keyword">AS</span> grade_uid, grade.gre <span class="hljs-keyword">AS</span> grade_gre, cla.cname <span class="hljs-keyword">AS</span> cla_cname <span class="hljs-keyword">FROM</span> grade INNER <span class="hljs-keyword">JOIN</span> stu <span class="hljs-keyword">ON</span> grade.uid = stu.id INNER <span class="hljs-keyword">JOIN</span> cla <span class="hljs-keyword">ON</span> grade.cid = cla.id <span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">15</span>:<span class="hljs-number">21</span>:<span class="hljs-number">29</span>,<span class="hljs-number">402</span> INFO sqlalchemy.engine.base.Engine () [(<span class="hljs-number">2</span>L, <span class="hljs-number">66</span>L, <span class="hljs-string">'yuwen'</span>), (<span class="hljs-number">5</span>L, <span class="hljs-number">66</span>L, <span class="hljs-string">'yuwen'</span>), (<span class="hljs-number">3</span>L, <span class="hljs-number">96</span>L, <span class="hljs-string">'shuxue'</span>), (<span class="hljs-number">2</span>L, <span class="hljs-number">50</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">3</span>L, <span class="hljs-number">60</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">4</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">5</span>L, <span class="hljs-number">96</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">1</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'wuli'</span>), (<span class="hljs-number">3</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'wuli'</span>), (<span class="hljs-number">4</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'wuli'</span>), (<span class="hljs-number">1</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'huaxue'</span>), (<span class="hljs-number">2</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'huaxue'</span>), (<span class="hljs-number">4</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'huaxue'</span>), (<span class="hljs-number">5</span>L, <span class="hljs-number">96</span>L, <span class="hljs-string">'huaxue'</span>)] >>> </code>
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<code class=" hljs oxygene">#查找有成绩同学的学好成绩和课程名，并进行排序 >>> print session.query(Grade.uid,Grade.gre,Cla.cname).<span class="hljs-keyword">join</span>(Stu,Grade.uid==Stud).<span class="hljs-keyword">join</span>(Cla,Grade.cid==Cla.id).order_by(Grade.uid,Grade.gre.<span class="hljs-keyword">desc</span>()).all() <span class="hljs-keyword">SELECT</span> grade.uid <span class="hljs-keyword">AS</span> grade_uid, grade.gre <span class="hljs-keyword">AS</span> grade_gre, cla.cname <span class="hljs-keyword">AS</span> cla_cname <span class="hljs-keyword">FROM</span> grade INNER <span class="hljs-keyword">JOIN</span> stu <span class="hljs-keyword">ON</span> grade.uid = stu.id INNER <span class="hljs-keyword">JOIN</span> cla <span class="hljs-keyword">ON</span> grade.cid = cla.id <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> grade.uid, grade.gre <span class="hljs-keyword">DESC</span> <span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">15</span>:<span class="hljs-number">34</span>:<span class="hljs-number">17</span>,<span class="hljs-number">902</span> INFO sqlalchemy.engine.base.Engine () [(<span class="hljs-number">1</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'wuli'</span>), (<span class="hljs-number">1</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'huaxue'</span>), (<span class="hljs-number">2</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'huaxue'</span>), (<span class="hljs-number">2</span>L, <span class="hljs-number">66</span>L, <span class="hljs-string">'yuwen'</span>), (<span class="hljs-number">2</span>L, <span class="hljs-number">50</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">3</span>L, <span class="hljs-number">96</span>L, <span class="hljs-string">'shuxue'</span>), (<span class="hljs-number">3</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'wuli'</span>), (<span class="hljs-number">3</span>L, <span class="hljs-number">60</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">4</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">4</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'huaxue'</span>), (<span class="hljs-number">4</span>L, <span class="hljs-number">76</span>L, <span class="hljs-string">'wuli'</span>), (<span class="hljs-number">5</span>L, <span class="hljs-number">96</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">5</span>L, <span class="hljs-number">96</span>L, <span class="hljs-string">'huaxue'</span>), (<span class="hljs-number">5</span>L, <span class="hljs-number">66</span>L, <span class="hljs-string">'yuwen'</span>)] >>> </code>
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或
<code class=" hljs avrasm">>>> query2=session<span class="hljs-preprocessor">.query</span>(Grade<span class="hljs-preprocessor">.uid</span>,Grade<span class="hljs-preprocessor">.gre</span>,Cla<span class="hljs-preprocessor">.cname</span>)<span class="hljs-preprocessor">.join</span>(Stu,Grade<span class="hljs-preprocessor">.uid</span>==Stid)<span class="hljs-preprocessor">.join</span>(Cla,Grade<span class="hljs-preprocessor">.cid</span>==Cla<span class="hljs-preprocessor">.id</span>)<span class="hljs-preprocessor">.order</span>_by(Grade<span class="hljs-preprocessor">.uid</span>,Grade<span class="hljs-preprocessor">.gre</span><span class="hljs-preprocessor">.desc</span>())<span class="hljs-preprocessor">.all</span>() SELECT grade<span class="hljs-preprocessor">.uid</span> AS grade_uid, grade<span class="hljs-preprocessor">.gre</span> AS grade_gre, cla<span class="hljs-preprocessor">.cname</span> AS cla_cname FROM grade INNER JOIN stu ON grade<span class="hljs-preprocessor">.uid</span> = stu<span class="hljs-preprocessor">.id</span> INNER JOIN cla ON grade<span class="hljs-preprocessor">.cid</span> = cla<span class="hljs-preprocessor">.id</span> ORDER BY grade<span class="hljs-preprocessor">.uid</span>, grade<span class="hljs-preprocessor">.gre</span> DESC <span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">15</span>:<span class="hljs-number">37</span>:<span class="hljs-number">33</span>,<span class="hljs-number">628</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> () >>> for re <span class="hljs-keyword">in</span> query2: ... print re<span class="hljs-preprocessor">.uid</span>,re<span class="hljs-preprocessor">.gre</span>,re<span class="hljs-preprocessor">.cname</span> ... <span class="hljs-number">1</span> <span class="hljs-number">76</span> wuli <span class="hljs-number">1</span> <span class="hljs-number">76</span> huaxue <span class="hljs-number">2</span> <span class="hljs-number">76</span> huaxue <span class="hljs-number">2</span> <span class="hljs-number">66</span> yuwen <span class="hljs-number">2</span> <span class="hljs-number">50</span> yingyu <span class="hljs-number">3</span> <span class="hljs-number">96</span> shuxue <span class="hljs-number">3</span> <span class="hljs-number">76</span> wuli <span class="hljs-number">3</span> <span class="hljs-number">60</span> yingyu <span class="hljs-number">4</span> <span class="hljs-number">76</span> yingyu <span class="hljs-number">4</span> <span class="hljs-number">76</span> huaxue <span class="hljs-number">4</span> <span class="hljs-number">76</span> wuli <span class="hljs-number">5</span> <span class="hljs-number">96</span> yingyu <span class="hljs-number">5</span> <span class="hljs-number">96</span> huaxue <span class="hljs-number">5</span> <span class="hljs-number">66</span> yuwen >>> </code>
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只需要把你要查的字段写在query()中就好了
<code class=" hljs oxygene">#查找成绩小于等于<span class="hljs-number">70</span>同学的学好成绩和课程名，并进行排序 >>>print session.query(Grade.uid,Grade.gre,Cla.cname).<span class="hljs-keyword">join</span>(Stu,Grade.uid==Stu.id).jn(Cla,Grade.cid==Cla.id).filter(Grade.gre<=<span class="hljs-number">70</span>).order_by(Grade.uid,Grade.gre.de()).all() <span class="hljs-keyword">SELECT</span> grade.uid <span class="hljs-keyword">AS</span> grade_uid, grade.gre <span class="hljs-keyword">AS</span> grade_gre, cla.cname <span class="hljs-keyword">AS</span> cla_cname <span class="hljs-keyword">FROM</span> grade INNER <span class="hljs-keyword">JOIN</span> stu <span class="hljs-keyword">ON</span> grade.uid = stu.id INNER <span class="hljs-keyword">JOIN</span> cla <span class="hljs-keyword">ON</span> grade.cid = cla.id <span class="hljs-keyword">WHERE</span> grade.gre <= %s <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> grade.uid, grade.gre <span class="hljs-keyword">DESC</span> <span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">15</span>:<span class="hljs-number">42</span>:<span class="hljs-number">06</span>,<span class="hljs-number">742</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">70</span>,) [(<span class="hljs-number">2</span>L, <span class="hljs-number">66</span>L, <span class="hljs-string">'yuwen'</span>), (<span class="hljs-number">2</span>L, <span class="hljs-number">50</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">3</span>L, <span class="hljs-number">60</span>L, <span class="hljs-string">'yingyu'</span>), (<span class="hljs-number">5</span>L, <span class="hljs-number">66</span>L, <span class="hljs-string">'yuwen'</span>)] >>> </code>
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或
<code class=" hljs r"><span class="hljs-comment">#用SQL语言来查询</span> >>> query = session.execute(<span class="hljs-string">"select uid from grade where cid = (select id fromla where cname='yuwen')"</span>) select uid from grade where cid = (select id from cla where cname=<span class="hljs-string">'yuwen'</span>) <span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">17</span>:<span class="hljs-number">12</span>:<span class="hljs-number">57</span>,<span class="hljs-number">395</span> INFO sqlalchemy.engine.base.Engine () >>> <span class="hljs-keyword">for</span> re <span class="hljs-keyword">in</span> query: <span class="hljs-keyword">...</span> print re.uid <span class="hljs-keyword">...</span> <span class="hljs-number">2</span> <span class="hljs-number">5</span> >>> </code>
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<code class=" hljs avrasm"><span class="hljs-preprocessor">#把学好为2成绩为100的学生成绩改为99</span>
>>> query5 = session<span class="hljs-preprocessor">.query</span>(Grade)
>>> query5<span class="hljs-preprocessor">.filter</span>(Grade<span class="hljs-preprocessor">.uid</span>==<span class="hljs-number">2</span>,Grade<span class="hljs-preprocessor">.gre</span>==<span class="hljs-number">100</span>)<span class="hljs-preprocessor">.update</span>({Grade<span class="hljs-preprocessor">.gre</span>:<span class="hljs-number">99</span>})
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">16</span>:<span class="hljs-number">28</span>:<span class="hljs-number">46</span>,<span class="hljs-number">485</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> UPDATE grade <span class="hljs-keyword">SET</span> gre=%s WHERE grade<span class="hljs-preprocessor">.uid</span> = %s <span class="hljs-keyword">AND</span> grade<span class="hljs-preprocessor">.gre</span> = %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">10</span> <span class="hljs-number">16</span>:<span class="hljs-number">28</span>:<span class="hljs-number">46</span>,<span class="hljs-number">486</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">99</span>, <span class="hljs-number">2</span>, <span class="hljs-number">100</span>)
<span class="hljs-number">1</span>L</code>Copy after login
此时没有提交还没有正在的改变
<code class=" hljs asciidoc"><span class="hljs-header">mysql> select * from grade where gre=100;
+----+------+------+------+</span>
<span class="hljs-header">| id | uid | cid | gre |
+----+------+------+------+</span>
<span class="hljs-header">| 15 | 2 | 3 | 100 |
+----+------+------+------+</span>
1 row in set (0.00 sec)
>>> session.commit()
mysql> select * from grade where gre=100;
Empty set (0.00 sec)
也可以这样搞
>>> session.query(Grade).filter(Grade.gre==99).update({Grade.gre:50})
</code>Copy after login
update里面使用的是字典类型
或这样搞
<code class=" hljs asciidoc">#用SQL语句把学语文的成绩都改为110
>>> session.execute("update grade set gre=110 where cid = (select id from cla ere cname=<span class="hljs-emphasis">'yuwen'</span>)")
<span class="hljs-code"> update grade set gre=110 where cid = (select id from cla where cname='yuwen')</span>
2016-05-10 17:15:59,383 INFO sqlalchemy.engine.base.Engine ()
<sqlalchemy.engine.result.ResultProxy object at 0xb5c895cc>
<span class="hljs-header">mysql> select * from grade where cid =(select id from cla where cname='yuwen');
+----+------+------+------+</span>
<span class="hljs-header">| id | uid | cid | gre |
+----+------+------+------+</span>
| 2 | 2 | 1 | 66 |
<span class="hljs-header">| 3 | 5 | 1 | 66 |
+----+------+------+------+</span>
2 rows in set (0.00 sec)
#提交后
>>> session.commit()
2016-05-10 17:16:18,223 INFO sqlalchemy.engine.base.Engine COMMIT
>>>
<span class="hljs-header">mysql> select * from grade where cid =(select id from cla where cname='yuwen');
+----+------+------+------+</span>
<span class="hljs-header">| id | uid | cid | gre |
+----+------+------+------+</span>
| 2 | 2 | 1 | 110 |
<span class="hljs-header">| 3 | 5 | 1 | 110 |
+----+------+------+------+</span>
2 rows in set (0.00 sec)</code>Copy after login
<code class=" hljs avrasm"><span class="hljs-preprocessor">#删除成绩为50的成绩记录</span> >>> session<span class="hljs-preprocessor">.query</span>(Grade)<span class="hljs-preprocessor">.filter</span>(Grade<span class="hljs-preprocessor">.gre</span>==<span class="hljs-number">50</span>)<span class="hljs-preprocessor">.delete</span>()</code>
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<code class=" hljs asciidoc">#删除选修英语的所有成绩记录，用SQL进行 >>> session.execute( "delete from grade where cid =(select id from cla where cme=<span class="hljs-emphasis">'yingyu'</span>)") 2016-05-10 16:55:55,472 INFO sqlalchemy.engine.base.Engine delete from grade where cid =(select id from cla where cname=<span class="hljs-emphasis">'yingyu'</span>) 2016-05-10 16:55:55,472 INFO sqlalchemy.engine.base.Engine () mysql> select * from grade where cid = (select id from cla where cname=<span class="hljs-emphasis">'yingyu'</span>) <span class="hljs-header"> -> ; +----+------+------+------+</span> <span class="hljs-header">| id | uid | cid | gre | +----+------+------+------+</span> | 5 | 5 | 3 | 96 | | 9 | 4 | 3 | 76 | <span class="hljs-header">| 14 | 3 | 3 | 60 | +----+------+------+------+</span> 3 rows in set (0.00 sec) >>> session.commit() 2016-05-10 16:56:33,075 INFO sqlalchemy.engine.base.Engine COMMIT >>> mysql> select * from grade where cid = (select id from cla where cname=<span class="hljs-emphasis">'yingyu'</span>) <span class="hljs-code"> -> ;</span> Empty set (0.00 sec)</code>
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级联删除：在relationship关联时要加上passive_deletes=True外键要加上ondelete=’CASCADE’,否则sqlalchemy不能级联删除
这些是多表连接的操作
单表的操作请看http://blog.csdn.net/u011573853/article/details/51355113
一些细节会在下面进行说明（事务，加锁，编码等）
http://blog.csdn.net/u011573853/article/details/51366124
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How to convert xml into pictures
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XML can be converted to images by using an XSLT converter or image library. XSLT Converter: Use an XSLT processor and stylesheet to convert XML to images. Image Library: Use libraries such as PIL or ImageMagick to create images from XML data, such as drawing shapes and text.
How to control the size of XML converted to images?
Apr 02, 2025 pm 07:24 PM
To generate images through XML, you need to use graph libraries (such as Pillow and JFreeChart) as bridges to generate images based on metadata (size, color) in XML. The key to controlling the size of the image is to adjust the values of the <width> and <height> tags in XML. However, in practical applications, the complexity of XML structure, the fineness of graph drawing, the speed of image generation and memory consumption, and the selection of image formats all have an impact on the generated image size. Therefore, it is necessary to have a deep understanding of XML structure, proficient in the graphics library, and consider factors such as optimization algorithms and image format selection.
How to open xml format
Apr 02, 2025 pm 09:00 PM
Use most text editors to open XML files; if you need a more intuitive tree display, you can use an XML editor, such as Oxygen XML Editor or XMLSpy; if you process XML data in a program, you need to use a programming language (such as Python) and XML libraries (such as xml.etree.ElementTree) to parse.
Recommended XML formatting tool
Apr 02, 2025 pm 09:03 PM
XML formatting tools can type code according to rules to improve readability and understanding. When selecting a tool, pay attention to customization capabilities, handling of special circumstances, performance and ease of use. Commonly used tool types include online tools, IDE plug-ins, and command-line tools.
