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我在一个 Python 脚本中有这个函数，该脚本已作为 Windows 服务与 NSSM 一起安装。当 Python 脚本正常运行（即不作为服务）时，将打印文件。但是，当它作为服务安装时，它不会打印。

打印是通过 opc-ua 外部触发的。

脚本作为服务安装时甚至可以打印吗？在作为服务安装时，我也没有遇到任何异常。有时我KeyboardInterrupt在循环之间睡觉时遇到异常。

def CheckOpcuaNode(latestPDF):
    client = Client("opc.tcp://192.168.202.90:4840/")
    try:
        client.connect()
        opcuaNode = client.get_node("ns=6;s=::AsGlobalPV:g_saveParameters.bPrintNow")
        Result = opcuaNode.get_value() 
        if Result == True:
             print("print file: %s" % str(latestPDF))
             os.startfile(latestPDF, "print")
             try:
                time.sleep(4)
             except KeyboardInterrupt:  # Ignore keyborditerruption
                print("ERROR KeyboardInterrupt while printing: %s" % sys.exc_info()[0])
             opcuaNode.set_attribute(ua.AttributeIds.Value, ua.DataValue(False))
    except:
            print("ERROR while checking if PDF shall be printed: %s" % sys.exc_info()[0])
    finally:
        client.disconnect()

def LatestPdf():
    return 'path\to\PDF\file.pdf'

if __name__ == '__main__':
while True:
    latestPdfFile = LatestPdf()
    if latestPdfFile != '':
        CheckOpcuaNode(latestPdfFile) # check If PLC has asked to print pdf file
    try:
        time.sleep(4)
    except KeyboardInterrupt:  # Ignore keyborditerruption
        print("ERROR KeyboardInterrupt between loops: %s" % sys.exc_info()[0])
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