PyHelper

by Alex Woodhead

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Python Interop for invocation, arguments and return types

What's new in this version

Multidimensional Property access from Python:

MultiGet - Retrieve the simple value or default from root or sub-key of multidimensional property. Optionally Use "None" for default value.
MultiSet - Set the value of multidimensional property at property root or sub-key
MultiKeys - Return a Python list of key names, from property root or property sub-key
MultiReplace - Replace the whole property data or a sub-key with a python dictionary
MultiMerge - Merge a python dictionary to root multidimensional property or sub-key
MultiDel - Delete whole multidimensional property data or just a subkey

PyHelper

Extra Python Interop for invocation, arguments and return types

Install:

IPM (ZPM): install alwo-pyhelper

TupleOut feature

When accessing IRIS methods from Python there are some useful output parameters that are convenient to also access in addition to a return type.
Consider the following example where we retrieve the text value found at a location in an HL7 message:

> import iris
> hl7=iris.cls("EnsLib.HL7.Message")._OpenId(145,0)
> hl7.GetValueAt("MSH:9.1")
'OUL'

As a non-empty value was retuned we can be reasonably confident that the function succeeded as intended.
But what happens if we try an invalid path?

> hl7.GetValueAt("<&$BadMSH:9.1")
''

An empty value was returned. However is this empty string valid, OR did something go wrong?
The class in our example, EnsLib.HL7.Message, provides a supporting OUTPUT parameter “pStatus” that will inform on the validity of value being returned.
Using the TupleOut feature we can access both the return value and this method success status in one operation.

> hl7=iris.cls("EnsLib.HL7.Message")._OpenId(145,0)
> val, status = iris.cls("alwo.PyHelper").TupleOut(hl7,"GetValueAt",['pStatus'],1,"<&$BadMSH:9.1")
> val==''
True
> iris.cls("%SYSTEM.Status").IsError(status)
1
> iris.cls("%SYSTEM.Status").DisplayError(status)
ERROR ErrGeneral: No segment found at path '<&$BadMSH'1

Returning ByRef literal as though Output

Historically, from objectscript parameters would be passed By-Reference for “dictionaries” for both input and output.
The Output directive evolved later and so there is much implementation using ByRef when the API intention was intented for what is now just Output.
Therefore it is useful to be able to access internal ByRef literals as though they has been implemented as accessible Output parameters.
Simply include the ByRef parameter name and it will be included in the output Tuple

> out,tsc=iris.cls("alwo.PyHelper").TupleOut("EnsLib.HL7.Message","%OpenId",['sc'],1,'er145999', 0)
> out
''
> iris.cls("%SYSTEM.Status").DisplayError(tsc)
ERROR #5809: Object to Load not found, class 'EnsLib.HL7.Message', ID 'er145999'1

Support for %objlasterror

In objectscript there is access to percent variables across method scope.
There are scenarios where detecting or accessing special variable %objlasterror is useful after calling a CORE or thirdparty API.
This utility facilitate Python context access to the %objlasterror variable as though it has been defined as an Output parameter, when invoking methods from Python.

> del _objlasterror
> out,_objlasterror=iris.cls("alwo.PyHelper").TupleOut("EnsLib.HL7.Message","%OpenId",['%objlasterror'],1,'er145999', 0)

iris.cls("%SYSTEM.Status").DisplayError(_objlasterror)

ERROR #5809: Object to Load not found, class 'EnsLib.HL7.Message', ID 'er145999'1

Arguments explained

Name	Description
objectOrReference	An instance of an iris object OR its classname (including package)
methodname	The method name to be called. Note this method can only be an instance method, if an instance was also passed in for the first argument
namesForOutput	This is a python list of string names corresponding to the specific OUTPUT arguments and the order you wish to return in the tuple. Note, where a method returns a non-null value, the first output is returned as the second tuple item. If there was no return from the method then the first output item occupies position one.
returnsValue	Indicate whether a return value is expected from the method invocation. “1” = Yes, “0” = No
args	Optionally one or more arguments. Where there arguments are Python Lists or Python Dictionaries, they will be specially handled to interop with IRIS List and Array types used by methods internally