For exemple, say i have the following code:
a = [[1],[2],[3]]
for c in a:
print(c)
for d in a:
print(d)
The current output of it is:
[1]
[1]
[2]
[3]
[2]
[1]
[2]
[3]
[3]
[1]
[2]
[3]
My question is whether it is possible to modify this code in a pretty way so that the output becomes like this:
[1]
[2]
[3]
[2]
[3]
[3]
In other words if it is possible, in a 'clean python', to have the inner loop to cover the list from the index the outer loop stopped.
I'd use the range and iterate over indexes:
a = [[1],[2],[3]]
for c in range(len(a)):
for d in range(c, len(a)):
print(a[d])
You can use enumerate and list slicing syntax (items[start:end:step], where start defaults to 0, end to items.length, and step to 1) to accomplish this:
items = [[1], [2], [3]]
for i, _ in enumerate(items):
for item in items[i:]:
print(item)
Another interesting (though less efficient) option would be to use itertools.accumulate in conjunction with sum:
from itertools import accumulate
items = [[1], [2], [3]]
for item in sum(accumulate(([x] for x in items[::-1])), [])[::-1]:
print(item)
You could use a list_iterator and branch off shallow copies as needed:
import copy
ia = iter(a)
for ai in ia:
print(ai)
for ai in copy.copy(ia):
print(ai)
# [1]
# [2]
# [3]
# [2]
# [3]
# [3]
