Using a global dictionary with threads in Python

Question

Is accessing/changing dictionary values thread-safe?

I have a global dictionary foo and multiple threads with ids id1, id2, ..

Answer 1

How it works?:

>>> import dis
>>> demo = {}
>>> def set_dict():
...     demo['name'] = 'Jatin Kumar'
...
>>> dis.dis(set_dict)
  2           0 LOAD_CONST               1 ('Jatin Kumar')
              3 LOAD_GLOBAL              0 (demo)
              6 LOAD_CONST               2 ('name')
              9 STORE_SUBSCR
             10 LOAD_CONST               0 (None)
             13 RETURN_VALUE

Each of the above instructions is executed with GIL lock hold and STORE_SUBSCR instruction adds/updates the key+value pair in a dictionary. So you see that dictionary update is atomic and hence thread safe.