If i call pwd() function from an expression inside a node’s parameter, Houdini will return the name of the node, containing the expression. But how can i request the full name (path+name) of the node, containing the expression ?

hou.pwd() gives you a hou.Node object. If you call hou.Node.path() you'll get the full path.
hou.pwd().path()

thank you for a such quick answer !