def common_count(t0, t1):
  "returns the length of the longest common prefix"
  for i, pair in enumerate(zip(t0, t1)):
    if pair[0] != pair[1]:
      return i
  return i
 
def group_by_longest_prefix(iterable):
  "given a sorted list of strings, group by longest common prefix"
  longest = 0
  out = []
 
  for t in iterable:
    if out: # for there are previous entries 
 
      # determine length of prefix in common with prev line
      common = common_count(t, out[-1])
 
      # if the current entry has a shorted prefix, output the previous 
      # entries then start a new group
      if common < longest:
        yield out
        longest = 0
        out = []
      # otherwise, just update the target prefix length
      else:
        longest = common
 
    # add the current entry to the group
    out.append(t)
 
  # ouput remaining entries as the last group
  if out:
    yield out
 
text = """
abcd
abdd
abde
"""
 
T = sorted(t.strip() for t in text.split("\n") if t)
 
for L in group_by_longest_prefix(T):
  print L
 
 

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