下面的代码，没有外部库为我工作。我在Python 2.7.9测试

CPU使用率

import os
    
CPU_Pct=str(round(float(os.popen('''grep 'cpu ' /proc/stat | awk '{usage=($2+$4)*100/($2+$4+$5)} END {print usage }' ''').readline()),2))
print("CPU Usage = " + CPU_Pct)  # print results

和Ram使用，总，使用和免费

import os
mem=str(os.popen('free -t -m').readlines())
"""
Get a whole line of memory output, it will be something like below
['             total       used       free     shared    buffers     cached\n', 
'Mem:           925        591        334         14         30        355\n', 
'-/+ buffers/cache:        205        719\n', 
'Swap:           99          0         99\n', 
'Total:        1025        591        434\n']
 So, we need total memory, usage and free memory.
 We should find the index of capital T which is unique at this string
"""
T_ind=mem.index('T')
"""
Than, we can recreate the string with this information. After T we have,
"Total:        " which has 14 characters, so we can start from index of T +14
and last 4 characters are also not necessary.
We can create a new sub-string using this information
"""
mem_G=mem[T_ind+14:-4]
"""
The result will be like
1025        603        422
we need to find first index of the first space, and we can start our substring
from from 0 to this index number, this will give us the string of total memory
"""
S1_ind=mem_G.index(' ')
mem_T=mem_G[0:S1_ind]
"""
Similarly we will create a new sub-string, which will start at the second value. 
The resulting string will be like
603        422
Again, we should find the index of first space and than the 
take the Used Memory and Free memory.
"""
mem_G1=mem_G[S1_ind+8:]
S2_ind=mem_G1.index(' ')
mem_U=mem_G1[0:S2_ind]

mem_F=mem_G1[S2_ind+8:]
print 'Summary = ' + mem_G
print 'Total Memory = ' + mem_T +' MB'
print 'Used Memory = ' + mem_U +' MB'
print 'Free Memory = ' + mem_F +' MB'

基于cpu使用代码@Hrabal，这是我使用的:

from subprocess import Popen, PIPE

def get_cpu_usage():
    ''' Get CPU usage on Linux by reading /proc/stat '''

    sub = Popen(('grep', 'cpu', '/proc/stat'), stdout=PIPE, stderr=PIPE)
    top_vals = [int(val) for val in sub.communicate()[0].split('\n')[0].split[1:5]]

    return (top_vals[0] + top_vals[2]) * 100. /(top_vals[0] + top_vals[2] + top_vals[3])

psutil库提供了各种平台上关于CPU、RAM等的信息:

psutil是一个模块，提供了一个接口，通过使用Python以可移植的方式检索正在运行的进程和系统利用率(CPU，内存)的信息，实现了ps、top和Windows任务管理器等工具提供的许多功能。 它目前支持Linux, Windows, OSX, Sun Solaris, FreeBSD, OpenBSD和NetBSD, 32位和64位架构，Python版本从2.6到3.5 (Python 2.4和2.5的用户可能使用2.1.3版本)。

一些例子:

#!/usr/bin/env python
import psutil
# gives a single float value
psutil.cpu_percent()
# gives an object with many fields
psutil.virtual_memory()
# you can convert that object to a dictionary 
dict(psutil.virtual_memory()._asdict())
# you can have the percentage of used RAM
psutil.virtual_memory().percent
79.2
# you can calculate percentage of available memory
psutil.virtual_memory().available * 100 / psutil.virtual_memory().total
20.8

以下是其他文档，提供了更多的概念和感兴趣的概念:

https://psutil.readthedocs.io/en/latest/

仅适用于Linux: 只有stdlib依赖的RAM使用的一行代码:

import os
tot_m, used_m, free_m = map(int, os.popen('free -t -m').readlines()[-1].split()[1:])

这是我前段时间整理的一些东西，它只是窗口，但可能会帮助你完成你需要完成的部分工作。

来自: “for sys available mem” http://msdn2.microsoft.com/en-us/library/aa455130.aspx

“单个进程信息和python脚本示例” http://www.microsoft.com/technet/scriptcenter/scripts/default.mspx?mfr=true

注意:WMI接口/进程也可用于执行类似的任务 我在这里没有使用它，因为当前的方法满足了我的需求，但是如果有一天需要扩展或改进它，那么可能需要研究可用的WMI工具。

python的WMI:

http://tgolden.sc.sabren.com/python/wmi.html

代码:

'''
Monitor window processes

derived from:
>for sys available mem
http://msdn2.microsoft.com/en-us/library/aa455130.aspx

> individual process information and python script examples
http://www.microsoft.com/technet/scriptcenter/scripts/default.mspx?mfr=true

NOTE: the WMI interface/process is also available for performing similar tasks
        I'm not using it here because the current method covers my needs, but if someday it's needed
        to extend or improve this module, then may want to investigate the WMI tools available.
        WMI for python:
        http://tgolden.sc.sabren.com/python/wmi.html
'''

__revision__ = 3

import win32com.client
from ctypes import *
from ctypes.wintypes import *
import pythoncom
import pywintypes
import datetime


class MEMORYSTATUS(Structure):
    _fields_ = [
                ('dwLength', DWORD),
                ('dwMemoryLoad', DWORD),
                ('dwTotalPhys', DWORD),
                ('dwAvailPhys', DWORD),
                ('dwTotalPageFile', DWORD),
                ('dwAvailPageFile', DWORD),
                ('dwTotalVirtual', DWORD),
                ('dwAvailVirtual', DWORD),
                ]


def winmem():
    x = MEMORYSTATUS() # create the structure
    windll.kernel32.GlobalMemoryStatus(byref(x)) # from cytypes.wintypes
    return x    


class process_stats:
    '''process_stats is able to provide counters of (all?) the items available in perfmon.
    Refer to the self.supported_types keys for the currently supported 'Performance Objects'
    
    To add logging support for other data you can derive the necessary data from perfmon:
    ---------
    perfmon can be run from windows 'run' menu by entering 'perfmon' and enter.
    Clicking on the '+' will open the 'add counters' menu,
    From the 'Add Counters' dialog, the 'Performance object' is the self.support_types key.
    --> Where spaces are removed and symbols are entered as text (Ex. # == Number, % == Percent)
    For the items you wish to log add the proper attribute name in the list in the self.supported_types dictionary,
    keyed by the 'Performance Object' name as mentioned above.
    ---------
    
    NOTE: The 'NETFramework_NETCLRMemory' key does not seem to log dotnet 2.0 properly.
    
    Initially the python implementation was derived from:
    http://www.microsoft.com/technet/scriptcenter/scripts/default.mspx?mfr=true
    '''
    def __init__(self,process_name_list=[],perf_object_list=[],filter_list=[]):
        '''process_names_list == the list of all processes to log (if empty log all)
        perf_object_list == list of process counters to log
        filter_list == list of text to filter
        print_results == boolean, output to stdout
        '''
        pythoncom.CoInitialize() # Needed when run by the same process in a thread
        
        self.process_name_list = process_name_list
        self.perf_object_list = perf_object_list
        self.filter_list = filter_list
        
        self.win32_perf_base = 'Win32_PerfFormattedData_'
        
        # Define new datatypes here!
        self.supported_types = {
                                    'NETFramework_NETCLRMemory':    [
                                                                        'Name',
                                                                        'NumberTotalCommittedBytes',
                                                                        'NumberTotalReservedBytes',
                                                                        'NumberInducedGC',    
                                                                        'NumberGen0Collections',
                                                                        'NumberGen1Collections',
                                                                        'NumberGen2Collections',
                                                                        'PromotedMemoryFromGen0',
                                                                        'PromotedMemoryFromGen1',
                                                                        'PercentTimeInGC',
                                                                        'LargeObjectHeapSize'
                                                                     ],
                                                                     
                                    'PerfProc_Process':              [
                                                                          'Name',
                                                                          'PrivateBytes',
                                                                          'ElapsedTime',
                                                                          'IDProcess',# pid
                                                                          'Caption',
                                                                          'CreatingProcessID',
                                                                          'Description',
                                                                          'IODataBytesPersec',
                                                                          'IODataOperationsPersec',
                                                                          'IOOtherBytesPersec',
                                                                          'IOOtherOperationsPersec',
                                                                          'IOReadBytesPersec',
                                                                          'IOReadOperationsPersec',
                                                                          'IOWriteBytesPersec',
                                                                          'IOWriteOperationsPersec'     
                                                                      ]
                                }
        
    def get_pid_stats(self, pid):
        this_proc_dict = {}
        
        pythoncom.CoInitialize() # Needed when run by the same process in a thread
        if not self.perf_object_list:
            perf_object_list = self.supported_types.keys()
                    
        for counter_type in perf_object_list:
            strComputer = "."
            objWMIService = win32com.client.Dispatch("WbemScripting.SWbemLocator")
            objSWbemServices = objWMIService.ConnectServer(strComputer,"root\cimv2")
        
            query_str = '''Select * from %s%s''' % (self.win32_perf_base,counter_type)
            colItems = objSWbemServices.ExecQuery(query_str) # "Select * from Win32_PerfFormattedData_PerfProc_Process")# changed from Win32_Thread        
        
            if len(colItems) > 0:        
                for objItem in colItems:
                    if hasattr(objItem, 'IDProcess') and pid == objItem.IDProcess:
                        
                            for attribute in self.supported_types[counter_type]:
                                eval_str = 'objItem.%s' % (attribute)
                                this_proc_dict[attribute] = eval(eval_str)
                                
                            this_proc_dict['TimeStamp'] = datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S.') + str(datetime.datetime.now().microsecond)[:3]
                            break

        return this_proc_dict      
                      
        
    def get_stats(self):
        '''
        Show process stats for all processes in given list, if none given return all processes   
        If filter list is defined return only the items that match or contained in the list
        Returns a list of result dictionaries
        '''    
        pythoncom.CoInitialize() # Needed when run by the same process in a thread
        proc_results_list = []
        if not self.perf_object_list:
            perf_object_list = self.supported_types.keys()
                    
        for counter_type in perf_object_list:
            strComputer = "."
            objWMIService = win32com.client.Dispatch("WbemScripting.SWbemLocator")
            objSWbemServices = objWMIService.ConnectServer(strComputer,"root\cimv2")
        
            query_str = '''Select * from %s%s''' % (self.win32_perf_base,counter_type)
            colItems = objSWbemServices.ExecQuery(query_str) # "Select * from Win32_PerfFormattedData_PerfProc_Process")# changed from Win32_Thread
       
            try:  
                if len(colItems) > 0:
                    for objItem in colItems:
                        found_flag = False
                        this_proc_dict = {}
                        
                        if not self.process_name_list:
                            found_flag = True
                        else:
                            # Check if process name is in the process name list, allow print if it is
                            for proc_name in self.process_name_list:
                                obj_name = objItem.Name
                                if proc_name.lower() in obj_name.lower(): # will log if contains name
                                    found_flag = True
                                    break
                                
                        if found_flag:
                            for attribute in self.supported_types[counter_type]:
                                eval_str = 'objItem.%s' % (attribute)
                                this_proc_dict[attribute] = eval(eval_str)
                                
                            this_proc_dict['TimeStamp'] = datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S.') + str(datetime.datetime.now().microsecond)[:3]
                            proc_results_list.append(this_proc_dict)
                    
            except pywintypes.com_error, err_msg:
                # Ignore and continue (proc_mem_logger calls this function once per second)
                continue
        return proc_results_list     

    
def get_sys_stats():
    ''' Returns a dictionary of the system stats'''
    pythoncom.CoInitialize() # Needed when run by the same process in a thread
    x = winmem()
    
    sys_dict = { 
                    'dwAvailPhys': x.dwAvailPhys,
                    'dwAvailVirtual':x.dwAvailVirtual
                }
    return sys_dict

    
if __name__ == '__main__':
    # This area used for testing only
    sys_dict = get_sys_stats()
    
    stats_processor = process_stats(process_name_list=['process2watch'],perf_object_list=[],filter_list=[])
    proc_results = stats_processor.get_stats()
    
    for result_dict in proc_results:
        print result_dict
        
    import os
    this_pid = os.getpid()
    this_proc_results = stats_processor.get_pid_stats(this_pid)
    
    print 'this proc results:'
    print this_proc_results

使用crontab运行不会打印pid

设置:*/1 * * * * sh dog.sh这一行在crontab -e

import os
import re

CUT_OFF = 90

def get_cpu_load():
    cmd = "ps -Ao user,uid,comm,pid,pcpu --sort=-pcpu | head -n 2 | tail -1"
    response = os.popen(cmd, 'r').read()
    arr = re.findall(r'\S+', response)
    print(arr)
    needKill = float(arr[-1]) > CUT_OFF
    if needKill:
        r = os.popen(f"kill -9 {arr[-2]}")
        print('kill:', r)

if __name__ == '__main__':
    # Test CPU with 
    # $ stress --cpu 1
    # crontab -e
    # Every 1 min
    # */1 * * * * sh dog.sh
    # ctlr o, ctlr x
    # crontab -l
    print(get_cpu_load())