Question

I am attempting to communicate with a device over serial using Pyserial. As commands need to be continually sent, they have to be placed in a while loop in Python.

I am currently using this code, and have taken a look at python process takes 100% CPU:

while True:
    #do some serial sending here
    time.sleep(0.2)

This code works. However, the sending speed is slow. I tried to make it faster by decreasing the sleep interval, but it seems to load the CPU a bit too much.

In short, is there a any way to effectively iterate over a while loop forever, while still maintaining a low consumption of CPU resources?

Answer 1

The slow CPU wasting part is the “do serial sending”. The while loop with just a short sleep will use negligible CPU.

Can you show the serial sending code. There may be a way to speed that up.

On this rather slow CPU I see this:

import time
while True: time.sleep(0.2)      # 0% CPU
while True: time.sleep(0.02)     # 0% CPU
while True: time.sleep(0.002)    # 0.5% CPU
while True: time.sleep(0.0002)   # 6% CPU
while True: time.sleep(0.00002)  # 18% CPU

Now do some extra work in the loop:

import time
while True: range(10000) and None; time.sleep(0.2)      # 1% CPU
while True: range(10000) and None; time.sleep(0.02)     # 15% CPU
while True: range(10000) and None; time.sleep(0.002)    # 60% CPU
while True: range(10000) and None; time.sleep(0.0002)   # 86% CPU

I ran those in the interpreter and stopped each while loop with ctrl-C.