Error message
objc[27880]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.
objc[27880]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.wrong reason
At first I thought the problem code, and later discovered that in fact is the more limiting macOS High Sierra operating system for multi-threaded.
Solution
Add in the environment variablesexport OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
- terminal
// 零时解决方法
// 在终端中执行以下命令，接着继续执行python程序
export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES// 永久解决方案
// 终端中执行以下命令
sudo echo "export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES" >> ~/.bash_profile && source ~/.bash_profile- PyCharm
// 在下面的选择中添加`OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES`，重启`PyCharm`即可
Run -> Edit Configuations... -> Environment variables 
