I've got a Python list of dictionaries, as follows:
a = [
{'main_color': 'red', 'second_color':'blue'},
{'main_color': 'yellow', 'second_color':'green'},
{'main_color': 'yellow', 'second_color':'blue'},
]
I'd like to check whether a dictionary with a particular key/value already exists in the list, as follows:
// is a dict with 'main_color'='red' in the list already?
// if not: add item
This question is related to
python
list
dictionary
Here's one way to do it:
if not any(d['main_color'] == 'red' for d in a):
# does not exist
The part in parentheses is a generator expression that returns True for each dictionary that has the key-value pair you are looking for, otherwise False.
If the key could also be missing the above code can give you a KeyError. You can fix this by using get and providing a default value. If you don't provide a default value, None is returned.
if not any(d.get('main_color', default_value) == 'red' for d in a):
# does not exist
Maybe this helps:
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 this in my_dictlist:
if this[key] == value:
return this
return {}
print in_dictlist(('main_color','red'), a)
print in_dictlist(('main_color','pink'), a)
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:
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!')
Result:
Exists!
Following works out for me.
#!/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'}
Perhaps a function along these lines is what you're after:
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
Source: Stackoverflow.com