如何检查python中是否存在值

how do check if a value exists in python

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我编写这个脚本是为了使用python从vCenter中提取性能数据。如果来宾不存在计数器，则脚本存在/中断。

我如何首先检查如果一个vm的计数器存在，那么分配该值：

下面是脚本：

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for vmpath in vmlist:
#Get the current performance manager object (it changes, so we can’t just instatiate it once)
pm = server.get_performance_manager()
#Get an actual VM object from the path
vm = server.get_vm_by_path(vmpath)
#Get the managed object reference for the VM, because the performance manager only accepts MoRefs
mor = vm._mor
#Get all the counters and their current values for that VM.
counterValues = pm.get_entity_counters(mor)
#Do some quick math on the values.
#They come to us in a convienent dictionary form.
#Values are descrobed here: http://www.vmware.com/support/developer/vc-sdk/visdk41pubs/ApiReference/virtual_disk_counters.html
if InitMyVariable.my_variable is None:
cpu_usage=counterValues['cpu.usage']
cpu_ready=counterValues['cpu.ready']
total_memory=counterValues['mem.granted']
memory_used=counterValues['mem.consumed']
Memory_usage=counterValues['mem.usage']
Memory_ballooned=counterValues['mem.vmmemctl']
Memory_swapped=counterValues['mem.swapped']
ReadLatency = counterValues['virtualDisk.totalReadLatency']
WriteLatency = counterValues['virtualDisk.totalWriteLatency']

#print them out.
print"VM Name",vm.get_property('name')
print"% CPU",cpu_usage
print"CPU Ready",cpu_ready
print"Total Memory",memory_used
print"% Memory Used",Memory_usage
print"Memory Ballooned",Memory_ballooned
print"Memory Swapped",Memory_swapped
print"Disk Read Latency",ReadLatency
print"Disk Write Latency",WriteLatency
print"——-"

server.disconnect()

这是错误：

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Traceback (most recent call last):
File"guest_perf.py", line 38, in <module>
ReadLatency = counterValues['virtualDisk.totalReadLatency']
KeyError: 'virtualDisk.totalReadLatency'

您可以这样使用in：

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if"virtualDisk.totalReadLatency" in counterValues:
doSomething()
else:
pass