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matplotlib error when running plotting in multiprocess

I am using python's Multiprocess.Pool to plot some data using multiple processes as follows:
class plotDriver:
def plot(self, parameterList):
numberOfWorkers = len(parameterList)
pool = Pool(numberOfWorkers)
pool.map(plotWorkerFunction, parameterList)
pool.close()
pool.join()
this is a simplified version of my class, the driver also contains other stuffs I choose to omit. The plotWorkderFunction is a single threaded function, which imports matplotlib and does all the plotting and setting figure styles and save the plots to one pdf file, and each worker is not interacting with the other.
I need to call this plot function multiple times since I have many parameterList, like following:
parameters = [parameterList0, parameterList1, ... parameterListn]
for param in parameters:
driver = PlotDriver()
driver.plot(param)
If parameters only contains one parameterList (the for loop only runs once), the code seems working fine. But it consistently fails whenever parameters contains more than one element, with the following error message happening on the second time in the loop.
Traceback (most recent call last):
File "plot.py", line 59, in <module>
plottingDriver.plot(outputFile_handle)
File "/home/yingryic/PlotDriver.py", line 69, in plot
pool.map(plotWrapper, workerParamList)
File "/home/yingryic/.conda/envs/pp/lib/python2.7/multiprocessing/pool.py", line 251, in map
return self.map_async(func.iterable, chunksize).get()
File "/home/yingryic/.conda/envs/pp/python2.7/multiprocessing/pool.py", line 567, in get
raise self._value
RuntimeError: In set_text: could not load glyph
X Error: BadIDChoice (invalid resouce ID chosen for this connection) 14
Extension: 138 (RENDER)
Minor opcode: 17 (RenderCreateGlyphSet)
Resouce id: 0xe00002
: Fatal IO error: client killed
any idea what is going wrong and how should I fix?

You can try placing import matplotlib into plotWorkerFunction() so that child processes will have their own copy of the module.

MemoryError in Python leads to empty pickle file

I'm working on a library-type checkout/checkin system. When the user clicks exit, the program calls a close_window function which dumps the current dictionary objects into pickle files before the window is destroyed.
def close_window(self):
if messagebox.askokcancel("Quit", "You want to close the program now?"):
patrons.dump_data()
self.master.destroy()
When the program is started again, it calls a load_data function which loads the pickled files. Somehow I ran into MemoryError when exiting the system and one of the pickled files was overwritten with an empty file. From the documentation, I gather that MemoryError occurs when the program creates too many objects and runs out of memory. I am not sure why this happened in my case since I am not dealing with large data. The pickled file that got overwritten was only 1 KB.
How can I ensure my pickled file is not overwritten with an empty file when MemoryError occurs? This can lead to serious data loss. I am new to programming and am using this project to learn. It is possible I've done something seriously wrong to lead to the memory error or maybe I just need more computer memory. In any case, it doesn't make sense to overwrite a saved file with an empty file whether memory error or not.
Exception in Tkinter callback
Traceback (most recent call last):
File "C:\Python34\lib\tkinter\__init__.py", line 1487, in __call__
return self.func(*args)
File "C:/Python34/Lib/site-packages/toolkit/main.py", line 435, in close_window
patrons.dump_data()
File "C:\Python34\Lib\site-packages\toolkit\patrons.py", line 20, in dump_data
pickle.dump(patronslist, f)
MemoryError
This error is partially discussed in MemoryError while pickling data in python. Here though, I got an empty file, not even a partial file. And I want to know if there is a workaround for this problem. Perhaps saving the pickled data to a temporary file. If no memory error occurred during the save, then the temp file can be used to overwrite the permanent file (but this may yet trigger another MemoryError right?).
I run Win7 x86, 3 GB RAM, Python 3.4.1

Based on Gerrat's comment above, I wonder if the following is a good way to go about this:
patrons.py
def dump_data():
with open("./pickled_dicts/temp_patrons.pkl", 'wb') as f:
global patronslist
pickle.dump(patronslist, f)
main.py
def close_window(self):
if messagebox.askokcancel("Quit", "You want to close the program now?"):
try:
patrons.dump_data()
os.remove("./pickled_dicts/patrons.pkl")
os.rename("./pickled_dicts/temp_patrons.pkl", "./pickled_dicts/patrons.pkl")
except MemoryError:
messagebox.showerror("Memory Problem", "Your computer experienced memory problem. Your last session was not saved.")
self.master.destroy()
Essentially, I am first saving the dictionary object to a temporary file (temp_patrons.pkl) which is renamed to my permanent file (patrons.pkl) assuming no MemoryError. If MemoryError, then the original patrons.pkl remains.

Get CPU temperature in python on windows

Basically, I want to read the CPU temperature with Python. Please explain in layman's terms as I have never done this on Windows before nor have I had to work with wmi.
This is what I have at the moment:
import wmi
w = wmi.WMI(namespace="root\wmi")
temperature_info = w.MSAcpi_ThermalZoneTemperature()[0]
print temperature_info.CurrentTemperature
(I got this code from this thread: Accessing CPU temperature in python)
However, on running the script, I get this error:
Traceback (most recent call last):
File "C:\Users\Ryan\Desktop\SerialSystemMonitor", line 4, in <module>
temperature_info = w.MSAcpi_ThermalZoneTemperature()[0]
File "C:\Python27\lib\site-packages\wmi.py", line 819, in query
handle_com_error ()
File "C:\Python27\lib\site-packages\wmi.py", line 241, in handle_com_error
raise klass (com_error=err)
x_wmi: <x_wmi: Unexpected COM Error (-2147217396, 'OLE error 0x8004100c', None, None)>
What can I do to get this to work?

According to the MSDN page on WMI Error Constants, the error you have received is:
WBEM_E_NOT_SUPPORTED
2147749900 (0x8004100C)
Feature or operation is not supported.
Presumably, then, your CPU does not provide temperature information through WMI. If your CPU doesn't expose this information, you're probably out of luck, at least as far as a straightforward solution in Python goes.
I assume you've tried the other option given in the answer you linked, using Win32_TemperatureProbe(); if you haven't, try it.

Just execute as Admin. It's work for me.

define parameter in update query in python psycopg2

This my python code which is used to perform update operation from reading the csv file. I tried with this also. It doesn't work out.
for i in cin:
try:
conn=psycopg2.connect("dbname=pharmaflare user=postgres")
cursor=conn.cursor()
cursor.execute("UPDATE pharmaflare_drug_interaction SET se_interaction ='%s' WHERE primary_drug ='%s' AND secondary_drug ='%s' AND side_effect ='%s'"%(i[3],i[0],i[1],i[2]))
conn.commit()
cursor.close()
conn.close()
#print "done",i[0],i[1],i[2],i[3]
except Exception as e:
cerr.writerow(i)
ferr.flush()
traceback.print_exc(file=sys.stdout)
continue
Here I am facing the exception like syntax error due to the QUOTE's problem:
Wherever the single quotes presents this exception arises.
Traceback (most recent call last):
File "<ipython console>", line 5, in <module>
ProgrammingError: syntax error at or near "S"
LINE 1: ...secondary_drug ='NEUER' AND side_effect ='MENIERE'S DISEASE'
Is there any alternative way available to define query statement without troubling the Quotes problem?

There are a couple ways to solve it. The easy/hack way to do it is to employ the re.escape() function. That function can be thought of as an equivalent to PHP's addslashes() function, though it pains me to make that comparison.
Having said that, my reading indicates psycopg2 takes advantage of PEP 249. If that's true, then you should be able to pass in parameterized queries and have it escape them for you.

Threaded Sessions expiring on SQLAlchemy?

This is difficult to describe or show much code for, but I'll try. Essentially I have a multi-threaded desktop app that will frequently handle the adding/removing/changing of tables in threads. From what I read, I should use scoped_session and pass that around to the various threads to do the work (I think?). Here're some basic code examples:
class SQL():
def __init__(self):
self.db = create_engine('mysql+mysqldb://thesqlserver')
self.metadata = MetaData(self.db)
self.SessionObj = scoped_session(sessionmaker(bind=self.db, autoflush=True))
db = SQL()
session = db.SessionObj()
someObj = Obj(val, val2)
session.add(someObj)
session.commit()
The above class is what I'm using as the general access of SQL stuff. After creating a new session, performing a query and update/add to it, upon the session.commit(), I get the following error:
Traceback (most recent call last):
File "core\taskHandler.pyc", line 42, in run
File "core\taskHandler.pyc", line 184, in addTasks
File "core\sqlHandler.pyc", line 35, in commit
File "sqlalchemy\orm\session.pyc", line 624, in rollback
File "sqlalchemy\orm\session.pyc", line 338, in rollback
File "sqlalchemy\orm\session.pyc", line 369, in _rollback_impl
File "sqlalchemy\orm\session.pyc", line 239, in _restore_snapshot
File "sqlalchemy\orm\state.pyc", line 252, in expire
AttributeError: 'NoneType' object has no attribute 'expire'
Then the next if another sql attempt goes through:
Traceback (most recent call last):
File "core\taskHandler.pyc", line 44, in run
File "core\taskHandler.pyc", line 196, in deleteTasks
File "sqlalchemy\orm\query.pyc", line 2164, in scalar
File "sqlalchemy\orm\query.pyc", line 2133, in one
File "sqlalchemy\orm\query.pyc", line 2176, in __iter__
File "sqlalchemy\orm\query.pyc", line 2189, in _execute_and_instances
File "sqlalchemy\orm\query.pyc", line 2180, in _connection_from_session
File "sqlalchemy\orm\session.pyc", line 729, in connection
File "sqlalchemy\orm\session.pyc", line 733, in _connection_for_bind
File "sqlalchemy\orm\session.pyc", line 249, in _connection_for_bind
File "sqlalchemy\orm\session.pyc", line 177, in _assert_is_active
sqlalchemy.exc.InvalidRequestError: This Session's transaction has been rolled back by a nested rollback() call. To begin a new transaction, issue Session.rollback() first.
That's about as much as I know and I think the best I can describe. Any ideas on what I'm supposed to be doing here? It's all mud to me. Thanks in advance!

The funny part is, you missed the most critical part of the answer you "ripped the code from", which is that there is a Python function in the middle, which is executing some abstract operation (it's labeled as func()). That code illustrates a transactional wrapper for a function, and in the above example you instead have an object method called commit() that isn't otherwise calling upon any additional operations with the Session.
Here you have kind of a session-holding object called SQL() that is not really adding any usefulness to your program and makes it needlessly complicated, and is probably also the source of the issue. Unless your application intends to connect to many different databases at different times, and use SQL() objects to represent that state, there's not much use in building a class called "SQL" that has an "engine" stuck onto it. Just stick the engine in a module somewhere, as well as your scoped_session().
The engine and scoped_session represent a pattern called the factory pattern - they are objects that create some other useful object, in this case scoped_session creates a Session, and the Engine is used internally by the Session to create a Connection with which to talk to the database. It doesn't make much sense to place the Session object as a sibling member along with Engine and scoped_session - you'd be carrying around either the factories (the Engine and scoped_session), or the object itself that they create (the Session), which all depends on what you're trying to do.
The Session itself, remember here we're talking about the thing the factories create (Session), not the factories themselves (Engine and scoped_session), is not in the least bit thread safe. It is something you usually create only local to a function - it shouldn't be global, and if you're in fact using a single SQL() object across threads that's probably the problem here. The actual error you're getting, I'm not really sure what that is and I could only have a better clue if I knew the exact version of SQLAlchemy in use here, though the randomness of the error suggests that you have some kind of threading issue where something is becoming None in one thread as another expects that same object to be present.
So what you need to establish in this program is when exactly a particular thread of execution begins, what it needs to do with the database as it proceeds, and then when it ends. When you can establish a consistent pattern for that, you would then link a single Session to this thread, which goes for the lifespan of that thread, and is never shared. All the objects which are produced by this session must also not be shared to other threads - they are extensions of the Session's state. If you have "worker threads" in use, those worker threads should load up their own data as needed, within their own Session. The Session represents a live database transaction and you generally want transactions local to a single thread.
As this is not a web application you might want to forego the usage of scoped_session, unless you do in fact have a place for a thread-local pattern to be used.