find particular value from list of dict in python

Question

I have a list of dictionaries like this:

s = [{'a':1,'b':2},{'a':3},{'a':2},{'a':1}]

remove duplicate value pair and I want a list of dictionaries like:

s = [{'a':1},{'a':3},{'a':2}]

Answer 1

Use list comprehension with filter a:

s = [{k: v for k, v in x.items() if k =='a'} for x in s]
print (s)
[{'a': 1}, {'a': 3}, {'a': 2}]

Answer 2

You could use a list comprehension adding new dictionary entries only if 'a' is contained:

[{'a':d['a']} for d in s if 'a' in d]
# [{'a': 1}, {'a': 3}, {'a': 2}]

Answer 3

You can try this.

s = [{'a':1,'b':2},{'a':3},{'a':2}]
s=[{'a':d['a']} for d in s]
# [{'a': 1}, {'a': 3}, {'a': 2}]

Answer 4

If you want to have a list of singleton dictionaries with only a keys, you can do this:

>>> [{'a': d.get('a')} for d in s]
[{'a': 1}, {'a': 3}, {'a': 2}]

But this just seems more suitable for a list of tuples:

>>> [('a', d.get('a')) for d in s]
[('a', 1), ('a', 3), ('a', 2)]

From the docs for dict.get:

Return the value for key if key is in the dictionary, else default. If default is not given, it defaults to None, so that this method never raises a Key Error.