I have a list of list. I am trying to convert it to a dictionary with the key being the n-element of the sublist and the value the first element of the list. I was able to achieve the expected results using loop but I am looking for a more elegant way to write it, using list comprehension for example
array = [
[1, 2, 3],
[5, 4, 8]
]
out = {}
for x in array:
y = x[0]
z = x[1:]
for k in z:
out[k] = y
Result:
out = {
2 : 1,
3 : 1,
4 : 5,
8 : 5
}
First, it helps to avoid creating additional variables when writing comprehensions.
Step 1: eliminate the variables:
out = {}
for x in array:
for k in x[1:]:
out[k] = x[0]
Step 2: replace the pattern
out = {}
for ...:
...
out[k] = v
by out = {k: v for ...}, where you repeat the for clauses in the same order as they appear in the original code:
out = {k: x[0] for x in array for k in x[1:]}
Did it over two lines to show what I did but this can all be put into one line.
D1 = {l[0]:l[1:] for l in array}
Out = {v[x]:k for k,v in D1.items() for x in range(len(v)) }
All in one line
Out = {v[x]:k for k,v in {l[0]:l[1:] for l in array}.items() for x in range(len(v)) }