根据字典中的键值检查列表中的值，Python

我有两个数据源，一个是列表，另一个是字典的列表，我的数据看起来像下面。

need_placeholder = ['1200', '1300', '1400']
ad_dict = [{"Name": "A", "ID": "1999"}, {"Name": "B", "ID": "1299"}, 
           {"Name": "C", "ID": "1400"}]

我需要检查是否 need_placeholders 项目等于 ID 值从 ad_dict. 这是我的脚本。

for item in need_placeholder:
    adpoint_key = item 
    for index, my_dict in enumerate(ad_dict):
        if my_dict["ID"] == adpoint_key:
            continue
        else:    
            print(f'No key exists for {adpoint_key}')

输出是：

No key exists for 1200
No key exists for 1200
No key exists for 1200
No key exists for 1300
No key exists for 1300
No key exists for 1300

我想要的输出是：

No key exists for 1200
No key exists for 1300

我怎样才能在不循环浏览字典或列表的情况下比较这些值呢？

解决方案：

你可以试试这个。

>>> need_placeholder = ['1200', '1300', '1400']
>>> ad_dict = [{"Name": "A", "ID": "1999"}, {"Name": "B", "ID": "1299"}, 
               {"Name": "C", "ID": "1400"}]
>>> keys={d['ID'] for d in ad_dict} # Set of all unique ID values
>>> [key for key in need_placeholder if not key in keys]
# ['1200', '1300']

你可以使用 itertools.filterfalse

list(filterfalse(lambda x:x in keys, need_placeholder))
# ['1200', '1300']

如果你不在乎秩序

set(need_placeholder)-keys
# {'1300', '1200'}

使用 all

>>> for key in need_placeholder:
...     if all(key != d['ID'] for d in ad_dict):
...         print(f'No key exists for {key}')
...
No key exists for 1200
No key exists for 1300

使用 for-else

>>> for key in need_placeholder:
...     for d in ad_dict:
...             if key==d['ID']:
...                     break
...     else:
...             print(f'No key {key}')
...
No key 1200
No key 1300