Gangmax Blog

Is Python dict thread safe?

From “here“ and “here“.

The short answer is yes, read the offical document about “global interpreter lock” from here.

However, in Google Python Style Guide, it suggests not to rely on this:

Do not rely on the atomicity of built-in types.

While Python’s built-in data types such as dictionaries appear to have atomic operations, there are corner cases where they aren’t atomic (e.g. if __hash__ or __eq__ are implemented as Python methods) and their atomicity should not be relied upon. Neither should you rely on atomic variable assignment (since this in turn depends on dictionaries).

Use the Queue module’s Queue data type as the preferred way to communicate data between threads. Otherwise, use the threading module and its locking primitives. Learn about the proper use of condition variables so you can use threading.Condition instead of using lower-level locks.

So you can choose what you want to do.