基础代码
****************************

.. include:: project.rst

.. include:: helloworld.rst

注释
===========================

.. tabs::

    .. tab:: 编程语言

        .. 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:: 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

    .. tab:: DSL

        .. tabs::

            .. tab:: jinja2

                .. 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:: 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:: 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:: 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::

    .. tab:: 编程语言

        .. tabs::

            .. code-tab:: py

                 def if_else_case(a: int):
                     if a == 0:
                         print("执行 if 语句块")
                     elif a == 1:
                         print("执行 else if 语句块")
                     else:
                         print("执行 else 语句块")

            .. tab:: Golang

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

    .. tab:: SQL

        .. tabs::

            .. tab:: mysql

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

循环
========================

   .. tabs::

       .. code-tab:: py

            for i in range(10):
                if i == 5:
                    continue
                print("位置1 执行 for 语句块 i:", i)

            i = 0
            b = True
            while b:
                print("位置2 执行 for 语句块 i:", i)
                i += 1
                if i >= 10:
                    b = False

            # 列表循环
            LIST = [1, 2, 3, 4, 5, 6, 7, 8, 9]
            for index, data in enumerate(LIST):
                print("位置3 执行 for 语句块 index: {}, data: {}".format(index, data))

            # 字典循环
            mp = {"A": "a", "B": "b", "C": "c"}
            for key, value in mp.items():
                print("位置4 执行 for 语句块 key: {}, value: {}".format(index, value))

            # 字符串循环
            STR = "今天天气很好"
            for index, char in enumerate(STR):
                print("位置5 执行 for 语句块 key: {}, char: {}".format(index, char))

            # 死循环
            j = 0
            while True:
                print("位置6 执行死循环 j:", j)
                j += 1
                if j >= 10:
                    break

       .. code-tab:: go

            package main

            import "fmt"

            func forCase(){
                for i := 0; i < 10; i++ {
                    if i == 5 {
                        continue
                    }
                    fmt.Println("位置1 执行 for 语句块 i:", i)
                }
                var i int
                var b = true
                for b {
                    fmt.Println("位置2 执行 for 语句块 i:", i)
                    i++
                    if i >= 10 {
                        b = false
                    }
                }

                // 切片循环
                list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
                for index, data := range list {
                    fmt.Printf("位置3 执行 for 语句块 index: %d, data: %d \n", index, data)
                }

                // 字典循环
                mp := map[string]string{"A": "a", "B": "b", "C": "c"}
                for key, value := range mp {
                    fmt.Printf("位置4 执行 for 语句块 key: %v, value: %v \n", key, value)
                }

                // 字符串循环
                str := "今天天气很好"
                for index, char := range str {
                    fmt.Printf("位置5 执行 for 语句块 index: %v, char: %v \n", index, string(char))
                }

                var j int
                for {
                    fmt.Println("位置6 执行 for 语句块 j:", j)
                    j++
                    if j >= 10 {
                        break
                    }
                }

                for i := 0; i < 2; i++ {
                    for j := 0; j < 2; j++ {
                        fmt.Printf("位置7 执行 for 语句块 i: %d, j: %d\n", i, j)
                    }
                }

            lab1:
                for i := 0; i < 2; i++ {
                    for j := 0; j < 2; j++ {
                        fmt.Printf("位置8 执行 for 语句块 i: %d, j: %d\n", i, j)
                        break lab1
                    }
                }
            }

       .. 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