Get a wrong cpu_frequence from raspberry pi in python-CodePudding

i want use python to get the cpu_freq value from raspberry pi 4B

def GetCpuInfo():
    # Get CPU frequence
    cpu_freq =open("/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq").read()
    return cpu_freq

when i print the cpu_freq data, the output always fixed in 1800000(it's the max cpu frequence 1.8Ghz of raspberry pi),but when each time i use the

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

this command in terminal,it give me the dynamic valve(600000-1800000) So why do i get wrong value when using the python? is it a wrong way to read this file?

CodePudding user response：

There's nothing wrong with your read().

The very act of starting Python can itself take enough cycles to cause the CPU to ramp up to full frequency, especially on a small system like a Pi.

To prevent that, add a delay to let it spool back down before you take your readings. For example:

import time

def GetCpuInfo():
    with open("/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq") as f:
        return f.read()

for _ in range(20):
    time.sleep(1)
    print(GetCpuInfo())