what is [o,]?

[landlord1984]

I am studying following teaching me about composition of class objects. What is o doing here?

def print_all_2(self):         def gen(o):             lAll = [o,]

from following codes:

class Node(object):     def __init__(self,sName):         self._lChildren = []         self.sName = sName     def __repr__(self):         return "<Node '{}'>".format(self.sName)     def append(self,*args,**kwargs):         self._lChildren.append(*args,**kwargs)     def print_all_1(self):         print(self)         for oChild in self._lChildren:             oChild.print_all_1()     def print_all_2(self):         def gen(o):             lAll = [o,]             while lAll:                 oNext = lAll.pop(0)                 lAll.extend(oNext._lChildren)                 yield oNext         for oNode in gen(self):             print(oNode)     oRoot = Node("root") oChild1 = Node("child1") oChild2 = Node("child2") oChild3 = Node("child3") oChild4 = Node("child4") oChild5 = Node("child5") oChild6 = Node("child6") oChild7 = Node("child7") oChild8 = Node("child8") oChild9 = Node("child9") oChild10 = Node("child10") oRoot.append(oChild1) oRoot.append(oChild2) oRoot.append(oChild3) oChild1.append(oChild4) oChild1.append(oChild5) oChild2.append(oChild6) oChild4.append(oChild7) oChild3.append(oChild8) oChild3.append(oChild9) oChild6.append(oChild10) # specify output from here onwards oRoot.print_all_1() oRoot.print_all_2() 

<Node 'root'> <Node 'child1'> <Node 'child4'> <Node 'child7'> <Node 'child5'> <Node 'child2'> <Node 'child6'> <Node 'child10'> <Node 'child3'> <Node 'child8'> <Node 'child9'> <Node 'root'> <Node 'child1'> <Node 'child2'> <Node 'child3'> <Node 'child4'> <Node 'child5'> <Node 'child6'> <Node 'child8'> <Node 'child9'> <Node 'child7'> <Node 'child10'>

I was curious and am still curious about [o,]. I have deleted the comma, made it as [o] and run the program again, it still works same. Is the comma necessary?

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I was curious and am still curious about [o,]. I have deleted the comma, made it as [o] and run the program again, it still works same. Is the comma necessary?

I was curious and am still curious about [o,]. I have deleted the comma, made it as [o] and run the program again, it still works same. Is the comma necessary?