SingleInstanceChecker class allows to check that only a single instance of a program is running.
To do it, you should create an object of this class. As long as this object is alive, calls to SingleInstanceChecker.IsAnotherRunning from other processes will return True.
As the object should have the life span as big as possible, it makes sense to create it either as a global or in App.OnInit . For example:
def OnInit(self):
self.name = "SingleApp-%s" % wx.GetUserId()
self.instance = wx.SingleInstanceChecker(self.name)
if self.instance.IsAnotherRunning():
wx.MessageBox("Another instance is running", "ERROR")
return False
frame = SingleAppFrame(None, "SingleApp")
frame.Show()
return True
Note that by default SingleInstanceChecker.CreateDefault is used to create the checker meaning that it will be initialized differently for different users and thus will allow different users to run the application concurrently which is usually the required behaviour. However if only a single instance of a program should be running system-wide, you need to call Create with a custom name which does not include GetUserId.
This class is implemented for Win32 and Unix platforms (supporting fcntl() system call, but almost all of modern Unix systems do) only.
__init__ | Default constructor. |
Create | Initialize the object if it had been created using the default constructor. |
CreateDefault | Calls Create with default name. |
IsAnotherRunning | Returns True if another copy of this program is already running and False otherwise. |
SingleInstanceChecker class allows to check that only a single instance of a program is running.
Possible constructors:
SingleInstanceChecker()
SingleInstanceChecker(name, path='')
Overloaded Implementations:
__init__ (self)
Default constructor.
You may call Create after using it or directly call IsAnotherRunning in which case CreateDefault will be implicitly used.
__init__ (self, name, path=’‘)
Constructor calling Create .
This constructor does exactly the same thing as Create but doesn’t allow to check for errors.
Parameters: |
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Initialize the object if it had been created using the default constructor.
Note that you can’t call Create more than once, so calling it if the non default constructor had been used is an error.
Parameters: |
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Return type: | bool |
Returns: | Returns False if initialization failed, it doesn’t mean that another instance is running – use IsAnotherRunning to check for it. |
Note
One of possible reasons while Create may fail on Unix is that the lock file used for checking already exists but was not created by the user. Therefore applications shouldn’t treat failure of this function as fatal condition, because doing so would open them to the possibility of a Denial of Service attack. Instead, they should alert the user about the problem and offer to continue execution without checking if another instance is running.
Calls Create with default name.
This method simply calls Create with a string composed of App.GetAppName and GetUserId.
Because this method uses App.GetAppName , it may only be called after the global application was constructed.
Return type: | bool |
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New in version 2.9.1.
Returns True if another copy of this program is already running and False otherwise.
Notice that if the object was created using the default constructor Create hadn’t been called before this method, it will call CreateDefault automatically.
Return type: | bool |
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