All possible combinations for 3 digits of list never the same

Question

I have a list that looks like:

A
B
C
D
E
F
G

How do I solve this to find all combinations for 3 digits. The same letter cannot be used in

Answer 1

To understand how the solution process works, try the following:

# get all combinations of n items from given list
def getCombinations(items, n):
    if len(items) < n: return [] # need more items than are remaining 
    if n == 0: return [''] # need no more items, return the combination of no items

    [fst, *rst] = items

    # all combinations including the first item in the list
    including = [fst + comb for comb in getCombinations(rst, n-1)]

    # all combinations excluding the first item in the list
    excluding = getCombinations(rst, n)

    both = including + excluding
    return both

x = ['a','b','c','d','e']
n = 3
print(getCombinations(x, n))
# ['abc', 'abd', 'abe', 'acd', 'ace', 'ade', 'bcd', 'bce', 'bde', 'cde']