How can I get list of values of keys in list of dicts in python?-CodePudding

I have a list of dicts:

[{"app1": "value1"},{"app2": "value2"},{"app1": "value3"},{"app1": "value4"}, {"app3": "value5"}]

How can I get all values of a certain key in a list? So for example for "app1" it should become something like:

{"app1":["value1", "value3", "value4"]}

For "app2" it just becomes:

 {"app2":["value2"]}

CodePudding user response：

Use a defaultdict with a nested for loop

from collections import defaultdict 

d = defaultdict(list)

lst = [{"app1": "value1"},{"app2": "value2"},{"app1": "value3"},{"app1": "value4"}, {"app3": "value5"}]

for i in lst:
    for k,v in i.items():
        d[k].append(v)

print(dict(d))

{'app1': ['value1', 'value3', 'value4'], 'app2': ['value2'], 'app3': ['value5']}

CodePudding user response：

You can use a list comprehension to get all the values for a given key:

>>> data = [{"app1": "value1"},{"app2": "value2"},{"app1": "value3"},{"app1": "value4"}, {"app3": "value5"}]
>>> {"app1": [d["app1"] for d in data if "app1" in d]}
{'app1': ['value1', 'value3', 'value4']}

And if you want to accumulate it all into a single dict that's just putting the list comprehension inside a dict comprehension:

>>> {k: [d[k] for d in data if k in d] for d in data for k in d}
{'app1': ['value1', 'value3', 'value4'], 'app2': ['value2'], 'app3': ['value5']}

CodePudding user response：

a = [{"app1": "value1"},{"app2": "value2"},{"app1": "value3"},{"app1": "value4"}, {"app3": "value5"}] #list of dicts

k = "app1" #key to look for

out = {k: []}
for item in a:
    for key in list(item):
        if key == k:
            out[k].append(item[key])

print(out)

{'app1': ['value1', 'value3', 'value4']}