The function parameter problem of Python (parameter is variable object)

See a piece of code today, where the function entry parameter has an argument of list, similar to the following:

def linux_monitor (pid=0, pidlist = []):
    Pidlist.append (PID)

There is a problem with test discovery, where you add print and call to discover (call two times with default parameter values):

 linux_monitor (pid=0, pidlist = []):
    Pidlist.append (PID)
    Print (PID)
Print (pidlist)

Linux_monitor ()
linux_monitor ()

The results are as follows:

At the second call, Pidlist is not empty.

So for variable parameters, it's important to note that problems such as lists can occur

We can work with the code as follows:

def linux_monitor (pid=0, pidlist = None):
if pidlist = = None:
Pidlist = []
Pidlist.append (PID)

We can try it.

The function parameter problem of Python (parameter is variable object)