blocks|key|907089|text|也许这会有帮助：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|907090|a+=+[{+'main_color':+'red',+'second_color':'blue'},
+++++{+'main_color':+'yellow',+'second_color':'green'},
+++++{+'main_color':+'yellow',+'second_color':'blue'}]

def+in_dictlist(key,+value,+my_dictlist):
++++for+entry+in+my_dictlist:
++++++++if+entry[key]+==+value:
++++++++++++return+entry
++++return+{}

print+in_dictlist('main_color','red',+a)
print+in_dictlist('main_color','pink',+a)|code-block|syntax|javascript|907091|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Maybe this helps:
<pre><code>a = [{ 'main_color': 'red', 'second_color':'blue'},
 { 'main_color': 'yellow', 'second_color':'green'},
 { 'main_color': 'yellow', 'second_color':'blue'}]

def in_dictlist(key, value, my_dictlist):
 for entry in my_dictlist:
 if entry[key] == value:
 return entry
 return {}

print in_dictlist('main_color','red', a)
print in_dictlist('main_color','pink', a)
</code></pre>

blocks|key|907024|text|也许你想要的就是下面这样的一个函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|907025|+def+add_unique_to_dict_list(dict_list,+key,+value):
++for+d+in+dict_list:
+++++if+key+in+d:
++++++++return+d[key]

++dict_list.append({+key:+value+})
++return+value|code-block|syntax|javascript|907026|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Perhaps a function along these lines is what you're after:

<pre><code> def add_unique_to_dict_list(dict_list, key, value):
 for d in dict_list:
 if key in d:
 return d[key]

 dict_list.append({ key: value })
 return value
</code></pre>

blocks|key|907125|text|基于@Mark+Byer的很好的答案，并遵循@Florent问题，只是为了表明它也适用于具有超过2个键的dics列表中的2个条件：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|907126|names+=+[]
names.append({'first':+'Nil',+'last':+'Elliot',+'suffix':+'III'})
names.append({'first':+'Max',+'last':+'Sam',+'suffix':+'IX'})
names.append({'first':+'Anthony',+'last':+'Mark',+'suffix':+'IX'})

if+not+any(d['first']+==+'Anthony'+and+d['last']+==+'Mark'+for+d+in+names):

++++print('Not+exists!')
else:
++++print('Exists!')|code-block|syntax|javascript|907127|结果：|907128|Exists!|907129|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Based on @Mark Byers great answer, and following @Florent question,
just to indicate that it will also work with 2 conditions on list of dics with more than 2 keys:

<pre><code>names = []
names.append({'first': 'Nil', 'last': 'Elliot', 'suffix': 'III'})
names.append({'first': 'Max', 'last': 'Sam', 'suffix': 'IX'})
names.append({'first': 'Anthony', 'last': 'Mark', 'suffix': 'IX'})

if not any(d['first'] == 'Anthony' and d['last'] == 'Mark' for d in names):

 print('Not exists!')
else:
 print('Exists!')
</code></pre>

Result:

<pre><code>Exists!
</code></pre>

blocks|key|1122152|text|这只是另一种方式来完成操作员的要求：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1122153|+if+not+filter(lambda+d:+d['main_color']+==+'red',+a):
+++++print('Item+does+not+exist')|code-block|syntax|javascript|1122154|filter会将列表过滤到OP正在测试的项目。然后，if条件会询问问题，“如果该项目不在那里”，则执行此块。|offset|length|style|CODE|1122155|entityMap^0|0|0|0|6|Q|2|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

Just another way to do what the OP asked:
<pre class="lang-py prettyprint-override"><code> if not filter(lambda d: d['main_color'] == 'red', a):
 print('Item does not exist')
</code></pre>
<code>filter</code> would filter down the list to the item that OP is testing for. The <code>if</code> condition then asks the question, &quot;If this item is not there&quot; then execute this block.

blocks|key|1122097|text|下面的内容对我来说很有效。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1122098|++++#!/usr/bin/env+python
++++a+=+[{+'main_color':+'red',+'second_color':'blue'},
++++{+'main_color':+'yellow',+'second_color':'green'},
++++{+'main_color':+'yellow',+'second_color':'blue'}]

++++found_event+=+next(
++++++++++++filter(
++++++++++++++++lambda+x:+x['main_color']+==+'red',
++++++++++++++++a
++++++++++++),
++++++#return+this+dict+when+not+found
++++++++++++dict(
++++++++++++++++name='red',
++++++++++++++++value='{}'
++++++++++++)
++++++++)

++++if+found_event:
++++++++print(found_event)

++++$python++/tmp/x
++++{'main_color':+'red',+'second_color':+'blue'}|code-block|syntax|javascript|1122099|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Following works out for me.
<pre><code> #!/usr/bin/env python
 a = [{ 'main_color': 'red', 'second_color':'blue'},
 { 'main_color': 'yellow', 'second_color':'green'},
 { 'main_color': 'yellow', 'second_color':'blue'}]

 found_event = next(
 filter(
 lambda x: x['main_color'] == 'red',
 a
 ),
 #return this dict when not found
 dict(
 name='red',
 value='{}'
 )
 )

 if found_event:
 print(found_event)

 $python /tmp/x
 {'main_color': 'red', 'second_color': 'blue'}
</code></pre>

blocks|key|1122239|text|我认为检查密钥是否存在会更好一些，因为一些评论者在首选答案enter+link+description+here下询问|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1122240|因此，我将在行尾添加一个小if子句：|1122241|input_key+=+'main_color'
input_value+=+'red'

if+not+any(_dict[input_key]+==+input_value+for+_dict+in+a+if+input_key+in+_dict):
++++print("not+exist")|code-block|syntax|javascript|1122242|我不确定，如果错误，但我认为OP要求检查键-值对是否存在，如果不存在，则应该添加键值对。|1122243|在这种情况下，我建议使用一个小函数：|1122244|a+=+[{+'main_color':+'red',+'second_color':+'blue'},
+++++{+'main_color':+'yellow',+'second_color':+'green'},
+++++{+'main_color':+'yellow',+'second_color':+'blue'}]

b+=+None

c+=+[{'second_color':+'blue'},
+++++{'second_color':+'green'}]

c+=+[{'main_color':+'yellow',+'second_color':+'blue'},
+++++{},
+++++{'second_color':+'green'},
+++++{}]


def+in_dictlist(_key:+str,+_value+:str,+_dict_list+=+None):
++++if+_dict_list+is+None:
++++++++#+Initialize+a+new+empty+list
++++++++#+Because+Input+is+None
++++++++#+And+set+the+key+value+pair
++++++++_dict_list+=+[{_key:+_value}]
++++++++return+_dict_list

++++#+Check+for+keys+in+list
++++for+entry+in+_dict_list:
++++++++#+check+if+key+with+value+exists
++++++++if+_key+in+entry+and+entry[_key]+==+_value:
++++++++++++#+if+the+pair+exits+continue
++++++++++++continue
++++++++else:
++++++++++++#+if+not+exists+add+the+pair
++++++++++++entry[_key]+=+_value
++++return+_dict_list


_a+=+in_dictlist("main_color",+"red",+a+)
print(f"{_a=}")
_b+=+in_dictlist("main_color",+"red",+b+)
print(f"{_b=}")
_c+=+in_dictlist("main_color",+"red",+c+)
print(f"{_c=}")|1122245|输出：|1122246|_a=[{'main_color':+'red',+'second_color':+'blue'},+{'main_color':+'red',+'second_color':+'green'},+{'main_color':+'red',+'second_color':+'blue'}]
_b=[{'main_color':+'red'}]
_c=[{'main_color':+'red',+'second_color':+'blue'},+{'main_color':+'red'},+{'second_color':+'green',+'main_color':+'red'},+{'main_color':+'red'}]|1122247|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/3897516/9620269^0|T|R|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@$A|13|B|14|1|15]]|C|$]]|$1|D|3|E|5|6|7|16|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|17|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|18|8|@]|9|@]|C|$]]|$1|M|3|N|5|6|7|19|8|@]|9|@]|C|$]]|$1|O|3|P|5|H|7|1A|8|@]|9|@]|C|$I|J]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@]|C|$]]|$1|S|3|T|5|H|7|1C|8|@]|9|@]|C|$I|J]]|$1|U|3|-4|5|6|7|1D|8|@]|9|@]|C|$]]]|V|$W|$5|X|Y|Z|C|$10|11]]]]

I think a check if the key exists would be a bit better, as some commenters asked under the preferred answer <a href="https://stackoverflow.com/a/3897516/9620269">enter link description here</a>
So, I would add a small if clause at the end of the line:
<pre class="lang-py prettyprint-override"><code>
input_key = 'main_color'
input_value = 'red'

if not any(_dict[input_key] == input_value for _dict in a if input_key in _dict):
 print(&quot;not exist&quot;)

</code></pre>
I'm not sure, if wrong but I think the OP asked to check, if the key-value pair exists and if not the key value pair should be added.
In this case, I would suggest a small function:
<pre class="lang-py prettyprint-override"><code>a = [{ 'main_color': 'red', 'second_color': 'blue'},
 { 'main_color': 'yellow', 'second_color': 'green'},
 { 'main_color': 'yellow', 'second_color': 'blue'}]

b = None

c = [{'second_color': 'blue'},
 {'second_color': 'green'}]

c = [{'main_color': 'yellow', 'second_color': 'blue'},
 {},
 {'second_color': 'green'},
 {}]


def in_dictlist(_key: str, _value :str, _dict_list = None):
 if _dict_list is None:
 # Initialize a new empty list
 # Because Input is None
 # And set the key value pair
 _dict_list = [{_key: _value}]
 return _dict_list

 # Check for keys in list
 for entry in _dict_list:
 # check if key with value exists
 if _key in entry and entry[_key] == _value:
 # if the pair exits continue
 continue
 else:
 # if not exists add the pair
 entry[_key] = _value
 return _dict_list


_a = in_dictlist(&quot;main_color&quot;, &quot;red&quot;, a )
print(f&quot;{_a=}&quot;)
_b = in_dictlist(&quot;main_color&quot;, &quot;red&quot;, b )
print(f&quot;{_b=}&quot;)
_c = in_dictlist(&quot;main_color&quot;, &quot;red&quot;, c )
print(f&quot;{_c=}&quot;)

</code></pre>
Output:
<pre><code>_a=[{'main_color': 'red', 'second_color': 'blue'}, {'main_color': 'red', 'second_color': 'green'}, {'main_color': 'red', 'second_color': 'blue'}]
_b=[{'main_color': 'red'}]
_c=[{'main_color': 'red', 'second_color': 'blue'}, {'main_color': 'red'}, {'second_color': 'green', 'main_color': 'red'}, {'main_color': 'red'}]
</code></pre>

I've got a Python list of dictionaries, as follows:

<pre><code>a = [
 {'main_color': 'red', 'second_color':'blue'},
 {'main_color': 'yellow', 'second_color':'green'},
 {'main_color': 'yellow', 'second_color':'blue'},
]
</code></pre>

I'd like to check whether a dictionary with a particular key/value already exists in the list, as follows:

<pre><code>// is a dict with 'main_color'='red' in the list already?
// if not: add item
</code></pre>

Check if value already exists within list of dictionaries?

Python

我有一个Python字典列表，如下所示：a = [    {'main_color': 'red', 'second_color':'blue'},    {'main_color': 'yellow', 'second_color':'green'},    {'main_color': 'yellow', 'second_color':'blue'},]我想检查列表中是否已经存在具有特定键/值

问检查字典列表中是否已存在值？
EN

回答 6

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问检查字典列表中是否已存在值？EN

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问检查字典列表中是否已存在值？
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