An Intro to Python Threading

A thread is an entity within a process that can be scheduled for execution. Also, it is the smallest unit of processing that can be performed in an OS (Operating System). In simple words, a thread is a sequence of such instructions within a program that can be executed independently of other code. For simplicity, you can assume that a thread is simply a subset of a process! A thread contains all this information in a Thread Control Block (TCB):

• Thread Identifier: Unique id (TID) is assigned to every new thread
• Stack pointer: Points to the thread’s stack in the process. The stack contains the local variables under the thread’s scope.
• Program counter: a register that stores the address of the instruction currently being executed by a thread.
• Thread state: can be running, ready, waiting, starting, or done.
• Thread’s register set: registers assigned to thread for computations.
• Parent process Pointer: A pointer to the Process control block (PCB) of the process that the thread lives on.

Consider the diagram below to understand the relationship between the process and its thread:

Multiple threads can exist within one process where:

• Each thread contains its own register set and local variables (stored in the stack).
• All threads of a process share global variables (stored in heap) and the program code.

Consider the diagram below to understand how multiple threads exist in memory:

This article covers the basics of multithreading in Python programming language. Just like multiprocessing, multithreading is a way of achieving multitasking. In multithreading, the concept of threads is used. Let us first understand the concept of thread in computer architecture.