level_order_traversal.py

def show_tree(tree):
	""" (Level order) Traverse and print parse tree
	"""
	queue = []
	queue.append(tree)

	while(len(queue) != 0):
		items = len(queue)

		while(items > 0):
			node = queue[0]
			queue.pop(0)

			kids = len(node.children)
			if(kids == 0):
				print(node.value, end = ' ')
			else:
				print(f"<{node.value}>", end = ' ')

			for i in range(kids):
				queue.append(node.children[i])
			items = items - 1
		print()
		
# Query - SELECT col_a, col_b FROM table_name;

# Output (manually spaced for clarity)

# <Query>
# SELECT <columns> 						FROM 	<name> 		<terminal>
# 		<name> 	<punctuation> 	<name> 			table_name 		;
# 		 col_a 			, 		col_b


# Query - SELECT col_a, col_b FROM table_name WHERE col_d = col_e AND col_f > 20;

# Output (manually spaced)

# <Query>
# SELECT <columns> 							FROM <name> 				<condition_list>
# 		<name> <punctuation> <name> 			table_name 			<condition> 			<comparator> 		<condition>
# 		col_a 		, 			col_b 							<name> <operator> <term> 		AND 		<name>  <operator>  <term>
# 																col_d 		= 	  <name> 					col_f 		> 		<integer>
# 																				   col_e 											20