idDiff.py

import minecraft_data.v1_9 as v1_9
mcDataItemAndBlockIds = {i['name'] for i in v1_9.items_list}.union({i['name'] for i in v1_9.blocks_list})
# itemIds are from https://jsfiddle.net/j9gfxeen/

# missing in jsfiddle
print(mcDataItemAndBlockIds.difference(itemIds))
{'piston_head', 'air', 'double_stone_slab', 'standing_sign', 'potatoes', 'double_stone_slab2', 'tripwire', 'flowing_lava', 'lit_redstone_ore', 'water', 'piston_extension', 'popped_chorus_fruit', 'unpowered_repeater', 'daylight_detector_inverted', 'unpowered_comparator', 'standing_banner', 'lit_redstone_lamp', 'melon_stem', 'double_wooden_slab', 'carrots', 'redstone_wire', 'pumpkin_stem', "dragon's_breath", 'unlit_redstone_torch', 'wall_banner', 'wall_sign', 'end_portal', 'lava', 'flowing_water', 'portal', 'powered_comparator', 'powered_repeater', 'fire'}

# missing in minecraft-data
print(set(itemIds).difference(mcDataItemAndBlockIds))
{'chorus_fruit_popped', 'chain_command_block', 'repeating_command_block', 'end_gateway', 'purpur_double_slab', 'purpur_stairs', 'chorus_plant', 'end_rod', 'end_bricks', 'purpur_pillar', 'grass_path', 'purpur_slab', 'dragon_breath', 'purpur_block', 'beetroots', 'chorus_flower'}