没有可选择的编译器怎么办？

public Vehicle getVehicle(){

22        System.out.println("给你一个交通工具！");

23        return null;

24    }

这个有点没明白，格式是修饰符+类名+方法名+形参列表+……。

这是什么方法命名啊？有这种格式吗

就是这个  \  符号怎么打出来 我只打得出 /

我的怎么不一样呢

老师这个 python课程的所有的PDF有统一下载的地址吗？还是必须一章一章的下载资料？

我直接就报错了

建议同学们私下去补这块儿知识，不用听老师的。老师就是照本宣科的在讲，听了容易混淆概念

这个查询用and只能查询一条数据  不能查询多条

为什么出错了

什么时候那个专门刷题的软件才能发布？

老师为什么显示错误？

from multiprocessing import Process, Queue

from time import sleep

class MyProcess(Process):

    def __init__(self,name,mq):

        Process.__init__(self)

        self.name = name

        self.mq = mq

    def run(self):

        print(f"Process:{self.name},start")

        print(f"get Data:{self.mq.get()}")

        sleep(3)

        print(f"Process:{self.name},end")

if __name__ == '__main__':

    mq = Queue()

    mq.put("1")

    mq.put("2")

    mq.put("3")

    p_list = []

    for i in range(3):

        p = MyProcess(f"p{i}",mq)

        p_list.append(p)

    for p in p_list:

        p.start()

        #p.join()

为什么要加join，不然会报错，mac

Traceback (most recent call last):

  File "<string>", line 1, in <module>

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/spawn.py", line 116, in spawn_main

Traceback (most recent call last):

  File "<string>", line 1, in <module>

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/spawn.py", line 116, in spawn_main

        exitcode = _main(fd, parent_sentinel)exitcode = _main(fd, parent_sentinel)

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/spawn.py", line 126, in _main

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/spawn.py", line 126, in _main

    self = reduction.pickle.load(from_parent)

      File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/synchronize.py", line 110, in __setstate__

self = reduction.pickle.load(from_parent)

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/synchronize.py", line 110, in __setstate__

    self._semlock = _multiprocessing.SemLock._rebuild(*state)

FileNotFoundError: [Errno 2] No such file or directory

    self._semlock = _multiprocessing.SemLock._rebuild(*state)

FileNotFoundError: [Errno 2] No such file or directory

Traceback (most recent call last):

  File "<string>", line 1, in <module>

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/spawn.py", line 116, in spawn_main

    exitcode = _main(fd, parent_sentinel)

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/spawn.py", line 126, in _main

    self = reduction.pickle.load(from_parent)

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/synchronize.py", line 110, in __setstate__

    self._semlock = _multiprocessing.SemLock._rebuild(*state)

FileNotFoundError: [Errno 2] No such file or directory

我的在sudoers中写入了还是不能执行sudo命令

里面这三个变量，users，username，userpwd报红，是因为没有连接到我的数据库嘛？？？