Logging and handling Python errors - Latest

Within the Python node, you have access to four different methods for logging. These methods all perform the same operation, but use a different log level. The methods are as follows:

• self.logInfo(msg)
• self.logLow(msg)
• self.logMedium(msg)
• self.logHigh(msg)

The severity of the log level with which the message is logged, in comparison to the LogLevel property on the Python node determine whether or not the message is actually written to the log.

These methods and corresponding log levels (as will be reported in the node’s log) are outlined in the following table:

self.logInfo("Beginning to process records")
rec = self.inputs[0].read()
if rec is None:
    self.logInfo("Finished processing records")
    return False
else:
    #process record

rec = self.inputs[0].read()
if rec is None:
    return False
else:
    self.recordNum = self.recordNum+1   optionalField = rec.field["optional"]
    if optionalField is None:
        self.logLow("field 'optional' is not set on record %d" % self.recordNum)
    else:
        #continue processing

rec = self.inputs[0].read()if rec is None:
return False
else:
    self.recordNum = self.recordNum+1
    requiredField = rec.field["required"]
    if requiredField is None:
        if self.continueOnRecordError:
            self.logMedium("field 'required' is not set on record %d" % self.recordNum)
        else:
            #continue processing

errors = False
self.dataIdx = inputs[0].metadata.find("Data")
self.lookupIdx = inputs[0].metadata.find("Lookup")
if self.dataIdx == -1:
    self.logHigh("Expected node input 'Data' does not exist")
errors = True

if self.lookupIdx == -1:
    self.logHigh("Expected node input 'Lookup' does not exist")
    errors = True
    
if errors:
    raise braininfo.BrainNodeException, "Required fields did not exist, unable to process node"

Any exception can be raised from the code within the initialize, finalize and pump methods and the node will handle them, failing the node appropriately.

In general, the easiest mechanism for forcing node failure, and reporting a message back to the node log is to raise a BrainNodeException. The following example shows where the required field specified in the InputFieldName property does not exist on the metadata:

idx = input.metadata.find(self.inputFieldName)
if idx == -1:
    raise braininfo.BrainNodeException, "Specified InputFieldName: %s does not exist on input: %s " % (self.inputFieldName, input.name)