Is the += operator thread-safe in Python?

Question

I want to create a non-thread-safe chunk of code for experimentation, and those are the functions that 2 threads are going to call.

c = 0

def increment():
          


        

Answer 1

It's easy to prove that your code is not thread safe. You can increase the likelyhood of seeing the race condition by using a sleep in the critical parts (this simply simulates a slow CPU). However if you run the code for long enough you should see the race condition eventually regardless.

from time import sleep
c = 0

def increment():
  global c
  c_ = c
  sleep(0.1)
  c = c_ + 1

def decrement():
  global c
  c_ = c
  sleep(0.1)
  c  = c_ - 1