The distinction between a process and a thread is foundational in computer science and systems programming.
Each process has one or more threads, but threads cannot exist outside a process.
| Term | Description |
|---|---|
| Process | An instance of a program in execution, with its own memory space, system resources, and execution context. |
| Thread | A unit of execution within a process. All threads in a process share the same memory and resources. |
| Analogy: |
- A process is like a house: self-contained, isolated, with its own address, rooms, and locks.
- A thread is like a person inside the house: they share the same environment, can talk freely (shared memory), but can interfere with each other.
In Practice
- Use processes when you want full isolation and need to bypass the GIL for CPU-bound tasks.
- Use threads when tasks are I/O-bound and sharing memory is beneficial.
Core Differences
| Aspect | Process | Thread |
|---|---|---|
| Memory | Each process has separate memory (heap, stack, etc.). | Threads share process memory (global Heap Memory) but have separate stacks. |
| Isolation | Fully isolated from other processes. | Not isolated: changes in memory affect all threads. |
| Communication | Requires inter-process communication (IPC) mechanisms (pipes, queues, sockets). | Communication is simpler via shared memory, but prone to race conditions. |
| Crash Impact | Crash in one process typically does not affect others. | Crash in one thread may take down the whole process. |
| Creation Overhead | Higher: requires setting up memory space, resources. | Lower: threads are more lightweight. |
| Context Switching | More costly: involves switching between separate memory contexts. | Faster: threads switch within the same process context. |
| Typical Use | For parallelism, running independent tasks. | For concurrency, especially when tasks need to share data or resources. |
from multiprocessing import Process
from threading import Thread