In Python, how can I detect whether the computer is on battery power?

Question

I'm playing around with pygame, and one thing I'd like to do is reduce the number of frames per second when the computer is on battery power (to lower the CPU usage and extend battery life).

How can I detect, from Python, whether the computer is currently on battery power?

I'm using Python 3.1 on Windows.

Answer 1

If you want to do it without win32api, you can use the built-in ctypes module. I usually run CPython without win32api, so I kinda like these solutions.

It's a tiny bit more work for GetSystemPowerStatus() because you have to define the SYSTEM_POWER_STATUS structure, but not bad.

# Get power status of the system using ctypes to call GetSystemPowerStatus  import ctypes from ctypes import wintypes  class SYSTEM_POWER_STATUS(ctypes.Structure):     _fields_ = [         ('ACLineStatus', wintypes.BYTE),         ('BatteryFlag', wintypes.BYTE),         ('BatteryLifePercent', wintypes.BYTE),         ('Reserved1', wintypes.BYTE),         ('BatteryLifeTime', wintypes.DWORD),         ('BatteryFullLifeTime', wintypes.DWORD),     ]  SYSTEM_POWER_STATUS_P = ctypes.POINTER(SYSTEM_POWER_STATUS)  GetSystemPowerStatus = ctypes.windll.kernel32.GetSystemPowerStatus GetSystemPowerStatus.argtypes = [SYSTEM_POWER_STATUS_P] GetSystemPowerStatus.restype = wintypes.BOOL  status = SYSTEM_POWER_STATUS() if not GetSystemPowerStatus(ctypes.pointer(status)):     raise ctypes.WinError() print('ACLineStatus', status.ACLineStatus) print('BatteryFlag', status.BatteryFlag) print('BatteryLifePercent', status.BatteryLifePercent) print('BatteryLifeTime', status.BatteryLifeTime) print('BatteryFullLifeTime', status.BatteryFullLifeTime) 

On my system that prints this (basically meaning "desktop, plugged in"):

ACLineStatus 1 BatteryFlag -128 BatteryLifePercent -1 BatteryLifeTime 4294967295 BatteryFullLifeTime 4294967295 

Answer 2

The most reliable way to retrieve this information in C is by using GetSystemPowerStatus. If no battery is present ACLineStatus will be set to 128. psutil exposes this information under Linux, Windows and FreeBSD, so to check if battery is present you can do this

>>> import psutil >>> has_battery = psutil.sensors_battery() is not None 

If a battery is present and you want to know whether the power cable is plugged in you can do this:

>>> import psutil >>> psutil.sensors_battery() sbattery(percent=99, secsleft=20308, power_plugged=True) >>> psutil.sensors_battery().power_plugged True >>>