AliceblueMiniModularity created by nloadholtes - https://repl.it/@nloadholtes/AliceblueMiniModularity

data.txt

Step G must be finished before step X can begin.
Step X must be finished before step B can begin.
Step A must be finished before step I can begin.
Step D must be finished before step H can begin.
Step O must be finished before step T can begin.
Step H must be finished before step C can begin.
Step S must be finished before step E can begin.
Step U must be finished before step M can begin.
Step M must be finished before step Z can begin.
Step R must be finished before step N can begin.
Step C must be finished before step Q can begin.
Step T must be finished before step P can begin.
Step I must be finished before step W can begin.
Step W must be finished before step N can begin.
Step P must be finished before step J can begin.
Step N must be finished before step F can begin.
Step Y must be finished before step J can begin.
Step J must be finished before step L can begin.
Step L must be finished before step E can begin.
Step E must be finished before step B can begin.
Step Q must be finished before step B can begin.
Step F must be finished before step K can begin.
Step V must be finished before step K can begin.
Step Z must be finished before step B can begin.
Step B must be finished before step K can begin.
Step G must be finished before step U can begin.
Step E must be finished before step V can begin.
Step A must be finished before step Z can begin.
Step C must be finished before step V can begin.
Step R must be finished before step B can begin.
Step Q must be finished before step Z can begin.
Step R must be finished before step K can begin.
Step T must be finished before step B can begin.
Step L must be finished before step B can begin.
Step M must be finished before step K can begin.
Step T must be finished before step Z can begin.
Step W must be finished before step B can begin.
Step I must be finished before step E can begin.
Step A must be finished before step M can begin.
Step V must be finished before step Z can begin.
Step Y must be finished before step B can begin.
Step Q must be finished before step F can begin.
Step W must be finished before step Y can begin.
Step U must be finished before step K can begin.
Step D must be finished before step F can begin.
Step P must be finished before step F can begin.
Step N must be finished before step L can begin.
Step H must be finished before step T can begin.
Step H must be finished before step L can begin.
Step C must be finished before step T can begin.
Step H must be finished before step I can begin.
Step Z must be finished before step K can begin.
Step L must be finished before step Z can begin.
Step Y must be finished before step K can begin.
Step I must be finished before step V can begin.
Step P must be finished before step K can begin.
Step P must be finished before step N can begin.
Step G must be finished before step D can begin.
Step I must be finished before step J can begin.
Step H must be finished before step K can begin.
Step L must be finished before step Q can begin.
Step D must be finished before step M can begin.
Step O must be finished before step V can begin.
Step R must be finished before step L can begin.
Step D must be finished before step W can begin.
Step M must be finished before step J can begin.
Step O must be finished before step R can begin.
Step N must be finished before step Z can begin.
Step Y must be finished before step V can begin.
Step W must be finished before step L can begin.
Step U must be finished before step Y can begin.
Step S must be finished before step V can begin.
Step M must be finished before step P can begin.
Step X must be finished before step A can begin.
Step A must be finished before step E can begin.
Step A must be finished before step L can begin.
Step A must be finished before step R can begin.
Step V must be finished before step B can begin.
Step P must be finished before step B can begin.
Step E must be finished before step F can begin.
Step T must be finished before step V can begin.
Step S must be finished before step R can begin.
Step T must be finished before step F can begin.
Step P must be finished before step Y can begin.
Step A must be finished before step C can begin.
Step J must be finished before step F can begin.
Step H must be finished before step B can begin.
Step C must be finished before step E can begin.
Step P must be finished before step E can begin.
Step D must be finished before step I can begin.
Step X must be finished before step F can begin.
Step T must be finished before step Q can begin.
Step J must be finished before step B can begin.
Step C must be finished before step B can begin.
Step P must be finished before step Q can begin.
Step H must be finished before step R can begin.
Step F must be finished before step B can begin.
Step T must be finished before step J can begin.
Step A must be finished before step W can begin.
Step N must be finished before step K can begin.
Step T must be finished before step E can begin.

main.py

def main():
  data = open("data.txt").readlines()
  output = []
  for line in data:
    first, second = line[5], line[36]
    try: 
      pos = output.index(first)
    except:
      output.append(first)
      pos = len(output) - 1
    if second < output[pos]:
      pos += 1
    if second not in output:
      output.insert(pos + 1, second)
  print("%s - %s" % (first, second))
  # Sorting 
  end = output.pop()
  start = output[0]
  output = output[1:]
  output.sort()
  output.insert(0, start)
  output.append(end)
  print("".join(output))

#main()

# Got this from reddit
from collections import defaultdict
# Edges
E = defaultdict(list)
# In-degree
D = defaultdict(int)
for line in open('data.txt'):
    words = line.split()
    x = words[1]
    y = words[7]
    E[x].append(y)
    D[y] += 1

for k in E:
    E[k] = sorted(E[k])
print(E)
print(D)

output = []
def drill(E, node=None):
  #print("---%s" % node)
  if not node:
    node = list(E.keys())[0]
    output.append(node)
  if node in E:
    for k in E[node]:
      if k in E and E[k] and k not in output:
        output.append(k)
      drill(E, k)

drill(E)
output.append((D-E.keys()).pop())
print("".join(output))
# for k in E:
#   print(k)
#   drill(E, k)

#recurse into E to get the correct order
# def drill(graph, edge_list, node):
#   for x in edge_list:
#     if x in graph:

#   if node in edge_list:
#     drill(

test.txt

Step C must be finished before step A can begin.
Step C must be finished before step F can begin.
Step A must be finished before step B can begin.
Step A must be finished before step D can begin.
Step B must be finished before step E can begin.
Step D must be finished before step E can begin.
Step F must be finished before step E can begin.