Buffering only selected points in PyQGIS

Question

I have a few random points that I generated within a polygon. I randomly selected one of the points and would like to buffer that point. In the case below, buffering will be applied to all points and not the selected point.

Do I need to create a new memory layer of the selected point first? If so, how?

#Generating random points within an "aoi" polygon file
pnts = processing.runAndLoadResults("native:randompointsinpolygons", {
                                    'INPUT': aoi,
                                    'POINTS_NUMBER': 10,
                                    'MIN_DISTANCE': 0,                                    
                                    'MIN_DISTANCE_GLOBAL': 0,                                    
                                    'MAX_TRIES_PER_POINT': 10,
                                    'SEED': None,
                                    'INCLUDE_POLYGON_ATTRIBUTES': True,
                                    'OUTPUT': 'memory:'
                                    }) 

#Randomly Choose one of the Points
processing.run("qgis:randomselection", {
                'INPUT': pnts['OUTPUT'],
                'METHOD': 0,
                'NUMBER':1
                })

#Buffering the point
pnt_buf = processing.runAndLoadResults("native:buffer", {
                           'INPUT':pnts,
                           'DISTANCE':3000,
                           'SEGMENTS':6,
                           'END_CAP_STYLE':0,
                           'JOIN_STYLE':1,
                           'MITER_LIMIT':3,
                           'DISSOLVE':True,
                           'SEPARATE_DISJOINT':False,
                           'OUTPUT':'memory:'
                           })

Answer 1

As per this question and answer Select feature by expression and run "native:buffer" on selection, works for "id" field but no other field in PyQGIS use a QgsProcessingFeatureSourceDefinition as follows (in the native:buffer call)

pnt_buf = processing.runAndLoadResults("native:buffer", {
    'INPUT': QgsProcessingFeatureSourceDefinition(pnts['OUTPUT'], selectedFeaturesOnly=True),
    'DISTANCE': 3000,
    'SEGMENTS': 6,
    'END_CAP_STYLE': 0,
    'JOIN_STYLE': 1,
    'MITER_LIMIT': 3,
    'DISSOLVE': True,
    'SEPARATE_DISJOINT': False,
    'OUTPUT': 'memory:'
    })

This will alter the input to the buffer algorithm on the fly.