这里的新手：我正在尝试依次执行一些代码，然后创建线程池并并行执行一些代码。并行执行完成后，我想串行执行更多代码。
例如...
import time
from multiprocessing import Pool
print("I only want to print this statement once")
def worker(i):
"""worker function"""
now = time.time()
time.sleep(i)
then = time.time()
print(now, then)
if __name__ == '__main__':
with Pool(3) as p:
p.map(worker, [1, 1, 1])
p.close()
print("Only print this once as well")
我想返回...
I only want to print this statement once
1533511478.0619314 1533511479.0620182
1533511478.0789354 1533511479.0791905
1533511478.0979397 1533511479.098235
Only print this once as well
但是它返回的是：
I only want to print this statement once
I only want to print this statement once
Only print this once as well
I only want to print this statement once
Only print this once as well
I only want to print this statement once
Only print this once as well
I only want to print this statement once
Only print this once as well
I only want to print this statement once
Only print this once as well
1533511478.0619314 1533511479.0620182
1533511478.0789354 1533511479.0791905
1533511478.0979397 1533511479.098235
Only print this once as well
因此，似乎每个池都要额外运行一次打印语句。
任何帮助将不胜感激！
答案 0 :(得分：0)
基于观察到的行为，我假设您使用的是NT / Windows操作系统。
看到所有这些打印件的原因是因为在Windows上使用了spawn启动策略。当“产生”新进程时，将启动一个新的Python解释器，它会接收应该执行的模块和功能。新解释器导入模块时，将执行顶层__main__函数。因此，重复打印。
只需在class YourViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, CustomCellDelegate {
@IBOutlet weak var tableView: UITableView?
override func viewDidLoad() {
super.viewDidLoad()
}
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 2
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let cell = tableView.dequeueReusableCell(withIdentifier: "identifier") as? CustomCell else {
return UITableViewCell()
}
cell.indexPath = indexPath
cell.delegate = self
return cell
}
func tableView(_ tableView: UITableView, editActionsForRowAt indexPath: IndexPath) -> [UITableViewRowAction]? {
return nil
}
func delete(for cell: CustomCell) {
let indexPath = cell.indexPath
print("doing action for cell at: \(indexPath!.row)")
// your implementation for action
// maybe delete a cell or whatever?
cell.hideDeleteActions()
}
}
protocol CustomCellDelegate: class {
func delete(for cell: CustomCell)
}
class CustomCell: UITableViewCell {
weak var delegate: CustomCellDelegate?
var indexPath: IndexPath!
@IBOutlet weak var buttonAction: UIButton?
@IBOutlet weak var constBtnDeleteAction: NSLayoutConstraint?
override func awakeFromNib() {
self.constBtnDeleteAction?.constant = 0
}
override func touchesEnded(_ touches: Set<UITouch>,
with event: UIEvent?) {
guard let point = touches.first?.location(in: self) else {
return
}
if self.point(inside: point, with: event) {
self.showDeleteActions()
}
}
func showDeleteActions() {
self.constBtnDeleteAction?.constant = 100
// Set it according to the button width
UIView.animate(withDuration: 0.3) {
self.layoutIfNeeded()
}
}
func hideDeleteActions() {
self.constBtnDeleteAction?.constant = 0
UIView.animate(withDuration: 0.3) {
self.layoutIfNeeded()
}
}
@IBAction func cellButtonAction() {
delegate?.delete(for: self)
}
}
中移动这些打印语句，您就不会再看到它们。