基本语法
****************************

.. include:: project.rst

.. include:: helloworld.rst

注释
===========================

.. tabs::

   .. tab:: python

       .. literalinclude:: /../../basicCode/comment/main.py
           :language: python

       .. note::

            开源代码参考

            * `sqlalchemy.engine.create::create_engine <https://github.com/sqlalchemy/sqlalchemy/blob/rel_2_0_35/lib/sqlalchemy/engine/create.py#L116>`_

   .. code-tab:: rust

        fn main() {
            // hello, world

            let lucky_number = 7; // I'm feeling lucky today
        }

   .. code-tab:: go

        /* 多行注释 */
        // 单行注释

   .. code-tab:: javascript

        /* 多行注释 */
        // 单行注释

   .. code-tab:: java

        /* 多行注释 */
        // 单行注释

   .. code-block:: jinja

        {# note: commented-out template because we no longer use this
            {% for user in users %}
                ...
            {% endfor %}
        #}

声明变量
==============================================

.. tabs::

   .. tab:: Python
        .. literalinclude:: /../../basicCode/variable/variable.py
            :language: python

   .. tab:: Rust
        .. literalinclude:: /../../basicCode/variable/variable.rs
            :language: rust

   .. tab:: Golang
        .. literalinclude:: /../../basicCode/variable/variable.go
            :language: go

   .. tab:: Javascript
        .. literalinclude:: /../../basicCode/variable/variable.js
            :language: javascript

常量
============================================

.. tabs::

   .. tab:: Python

        .. literalinclude:: /../../reference/basic/constant/constant.py
            :language: python

   .. tab:: Rust

        .. literalinclude:: /../../reference/basic/constant/constant.rs
            :language: rust

   .. tab:: Golang
        .. literalinclude:: /../../reference/basic/constant/constant.go
            :language: go

   .. tab:: Javascript
        .. literalinclude:: /../../reference/basic/constant/constant.js
            :language: javascript

字符串
=========================================

.. tabs::

   .. tab:: Python
        .. literalinclude:: /../../reference/basic/string/_string.py
            :language: python

    .. tab:: Rust
        .. literalinclude:: /../../reference/basic/string/string.rs
            :language: rust

   .. tab:: Golang
        .. literalinclude:: /../../reference/basic/string/string.go
            :language: go

   .. tab:: Javascript
        .. literalinclude:: /../../reference/basic/string/string.js
            :language: javascript

.. include:: list.rst
.. include:: array.rst
.. include:: dict.rst
.. include:: typing.rst

条件判断
===============================================

.. tabs::

    .. code-tab:: py

        .. literalinclude:: /../../reference/basic/condition/condition.py
            :language: python

    .. tab:: Golang

        .. literalinclude:: /../../reference/basic/condition/condition.go
            :language: go

    .. tab:: mysql

        .. literalinclude:: /../../reference/basic/condition/condition.sql
            :language: mysql

循环
========================

   .. tabs::

       .. tab:: Python

           .. literalinclude:: /../../reference/basic/for/for.py
               :language: python

       .. tab:: Rust

           .. literalinclude:: /../../reference/basic/for/for.rs
               :language: rust

       .. tab:: Golang

           .. literalinclude:: /../../reference/basic/for/for.go
               :language: golang

       .. tab:: MySQL

           while

           .. literalinclude:: /../../reference/basic/for/mysql/while.sql
               :language: mysql

           loop

           .. literalinclude:: /../../reference/basic/for/mysql/loop.sql
               :language: mysql


switch
============================

.. tabs::

    .. code-tab:: py

        # match表面上像C、Java或JavaScript中的switch语句，但其实它更像Rust或Haskell中的模式匹配。

        def http_error(status):
            match status:
                case 400:
                    return "Bad request"
                case 404:
                    return "Not found"
                case 418:
                    return "I'm a teapot"
                case _:
                    return "Something's wrong with the internet"

    .. tab:: Go

        .. literalinclude:: /../../reference/basic/switch/main.go
            :language: go

    .. code-tab:: mysql

        create procedure proc_statement_case (in parameter int)
        begin
            declare var int;
            set var=parameter+1;
            case var
                when 0 then
                insert into userinfo values(4, 'zhangsan4', 18);
                when 1 then
                insert into userinfo values(5, 'zhangsan5', 18);
                else
                insert into userinfo values(6, 'zhangsan6', 18);
                end case;
        end;

异常
======================

.. tabs::

   .. tab:: Python

        .. literalinclude:: error/main.py
            :language: python

        **else子句**

        try … except 语句有一个可选的 else 子句，在使用时必须放在所有的 except 子句后面。对于在try 子句不引发异常 时必须执行的代码来说很有用。例如:

        .. code-block:: python

            for arg in sys.argv[1:]:
                try:
                    f = open(arg, 'r')
                except OSError:
                    print('cannot open', arg)
                else:
                    print(arg, 'has', len(f.readlines()), 'lines')
                    f.close()

        **finally**

        .. code-block:: pycon

            >>> try:
            ...     raise KeyboardInterrupt
            ... finally:
            ...     print('Goodbye, world!')
            ...
            Goodbye, world!
            KeyboardInterrupt
            Traceback (most recent call last):
              File "<stdin>", line 2, in <module>

        如果存在 finally 子句，则 finally 子句将作为 try 语句结束前的最后一项任务被执行。
        finally 子句不论 try 语句是否产生了异常都会被执行。

        **异常链**

        raise 语句允许可选的 from 子句，它启用了链式异常。 例如::

            # exc must be exception instance or None.
            raise RuntimeError from exc

        .. tip::

            用途: 转换异常

        禁用异常链可使用 from None 习语

        **打印异常内容**

        .. code-block:: python

            import traceback

            try:
                print(1/0)
            except Exception:
                # 输出到控制台
                traceback.print_exc()
                # 保存到变量
                err = traceback.format_exc()

   .. tab:: Golang

        .. literalinclude:: error/main.go
            :language: go

   .. tab:: Mysql

        .. literalinclude:: error/main.sql
            :language: mysql

.. include:: import.rst
.. include:: function.rst
.. include:: trycatch.rst
.. include:: debugger.rst
.. include:: interface.rst
.. include:: T.rst