CODEWITHSUNDEEP
pythonmultithreadinglocking
FrankBr
FrankBr

Reputation: 896

thread lock in Python

I code a python script using a gstreamer plugin. It returns me a segmentation fault because a race to access to a shared file (which one thread writes and the gstremear one createsreads) happens. I wanna lock it during the writing phase, reading the Python doc. I coded in the __init__:

self.lock=thread.allocate_lock()

and then in another function in the same class of __init__:

self.lock.acquire()
try:
    plt.savefig(self.filepath_image,transparent=True)
finally:
    self.lock.release()

Upvotes: 0

Views: 1986

Answers (1)

bereal
bereal

Reputation: 34282

Ok, if I understand your situation correct, you may want to make the savefig operation atomic, which can be done like this:

import os, shutil, tempfile    

tempfile = os.path.join(tempfile.tempdir, self.filepath_image)
#          ^^^ or simply self.filepath_image + '.tmp'
try:
    plt.savefig(tempfile,transparent=True)     # draw somewhere else 
    shutil.move(tempfile, self.filepath_image) # move to the target
finally:
    if os.path.exists(tempfile):
        os.remove(tempfile)

shutil.move is atomic (at least, in Unix, inside the same FS), so nobody will access the destination file until it's ready for usage.

Upvotes: 1

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