I have 2 lists:
x = [a,b]
y = [c,d]
and I want to create a list of dictionary like this:
dict = [{ex1:a,ex2:c},{ex1:b,ex2:c},{ex1:a,ex2:d},{ex1:b,ex2:d}]
How can I do that in a simple way?
2 Answers
Here's one way to do it using a list comprehension:
lst = [{'ex1': j, 'ex2': i} for i in y for j in x]
If the list items are strings, you'll get:
print(lst)
# [{'ex2': 'c', 'ex1': 'a'}, {'ex2': 'c', 'ex1': 'b'}, {'ex2': 'd', 'ex1': 'a'}, {'ex2': 'd', 'ex1': 'b'}]
Comments
There is a package called itertools which provides many methods to make this kind of things easy. I assume you might have not only one list, but eventually more, so you can put them in another list my_lists, take their product, and the rest of the thing is just making it a dict in the desired format, i.e. with keys like ex1.
Edit:
Here is the same with list comprehension:
[dict(('ex%u' % (i[0] + 1), i[1]) for i in enumerate(co))
for co in itertools.product(*my_lists)]
And was like this with map:
import itertools
x = ['a', 'b']
y = ['c', 'd']
my_lists = [x, y]
list_of_dicts = (
list(
map(
lambda co:
dict(
map(
lambda i:
('ex%u' % (i[0] + 1), i[1]),
enumerate(co)
)
),
itertools.product(*my_lists)
)
)
)
9 Comments
Paul Rooney
your formatting is unconventional and makes this code almost impossible to read.
juanpa.arrivillaga
Please at least try to stick to Python style conventions. In Python, a comprehension is almost always better than an equivalent
map with lambda from a readability perspective, and will likely perform better too. For the record, I did not downvote, since this does add a valuable generalization with product... just improve the style...
deeenes
thanks Paul for pointing this out. I thought about it a lot how to format multiple nested maps, and this was the most clear I could come up with. but I would be extremely grateful if you could show me a better way (just put this in a pastebin, if you have 2 minutes for me)
juanpa.arrivillaga
The answer is don't use multiple maps.
Paul Rooney
Also just use string literals
'ex1' and 'ex2' rather than trying to be clever with enumerate. |
dict, which is a builtin, as a variable name is not good practice and can cause problems elsewhere in your code.