Python: Combinations of parent-child hierarchy

Question

For a child-parent relationship table (csv), I am trying to gather possible parent to child relationship combination chains using all data in the table. I am trying against

Answer 1

I'm not sure if this is the most efficient way to do it (but reading the file in again on every row would be worse).

find= 'A' #The child for which the code should find all possible parent relationships
sequences = set(find)

# we'll build up a chain for every relationship, then strip out un-needed ones later
with open('testing.csv','r') as f:     #testing.csv = child,parent table (above example)
    for row in f:
        child, parent = row.strip().split(',')
        sequences.add(parent + '|' + child)
        for c in sequences.copy():  
            if c[0] == child:
                sequences.add(parent + '|' + c)


# remove any that don't end with our child:
sequences = set(s for s in sequences if s.endswith(find))

# get all shorter chains when we have a longer one
extra = set()
for g1 in sequences:
    for g2 in sequences:
        if g2[2:] == g1:
            extra.add(g1)

# remove the shorter chains
sequences.difference_update(extra)

for chain in sequences:
    print(chain)

Results:

D|C|A
D|C|B|A
D|B|A