Atomic operations

An operation is atomic if it cannot be interrupted. In Python, these operations are atomic:

• reading or replacing a single instance attribute
• reading or replacing a single global variable
• fetching an item from a list
• modifying a list in-place (e.g. with append)
• fetching an item from a dictionary
• modifying a dictionary in-place

Examples of things which are not atomic:

• Read a variable and write a new value back to it