I have a set of indices in a list:
[2 0 3 4 5]
And I want to replace them by values stored in another list:
[a b c d e f g]
And output:
[c a d e f]
I tried this code:
for line in indices:
print(line)
for value in line:
value = classes[value]
print(line)
break
which prints the original list twice. Is there a way to replace the elements or am I forced to create a new list of lists?
This looks like a good place to use a list comprehension, try this - the idiomatic solution:
idxs = [2, 0, 3, 4, 5]
chars = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
[chars[i] for i in idxs]
=> ['c', 'a', 'd', 'e', 'f']
Of course, we could do the same using explicit looping as you intended, but it's not as cool as the previous solution:
ans = []
for i in idxs:
value = chars[i]
ans.append(value)
ans
=> ['c', 'a', 'd', 'e', 'f']
And as a final alternative - I don't know why you want to "replace the elements" in the input list (as stated in the question), but sure, that's also possible, but not recommended - it's simpler and cleaner to just create a new list with the answer (as shown in the two previous snippets), instead of changing the original input:
for pos, val in enumerate(idxs):
idxs[pos] = chars[val]
idxs
=> ['c', 'a', 'd', 'e', 'f']
idxs = [2, 0, 3, 4, 5]
chars = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
map(lambda x : chars[x],idxs)
=> ['c', 'a', 'd', 'e', 'f']
Or
reduce(lambda x,y: x+[chars[y]],idxs,[])
=> ['c', 'a', 'd', 'e', 'f']
you can also use chr() function which converts int to characters(ascii table)
>>> a = [2 0 3 4 5]
>>> [chr(i+97) for i in a]
['c', 'a', 'd', 'e', 'f']
a are just indices
print. What do you mean by "replacing the elements"? you don't want to do that! leave the input lists alone, and simply create a new one with the answer, as shown in my solution.