import ast


source = '1+2-3'
root = ast.parse(source)

# col_offset should be 0 for both BinOp-s

def print_node(node, level=0):
    print("  " * level, node.__class__.__name__, end="")
    
    for att in node._attributes:
        print(", " + att + "=" + str(getattr(node, att)), end="")
        
    print()
        
    for child in ast.iter_child_nodes(node):
        print_node(child, level+1)

print_node(root)