Try graphlib.TopologicalSort

top_sort.py

>>> from graphlib import TopologicalSorter

>>> data = {"A": ["B", "D"], "B": [], "D": [], "C": ["A"]}
>>> ts = TopologicalSorter(data)
>>> for a in ts.static_order():
...     print(a)
...
B
D
A
C

>>> data = {"A": ["B", "D"], "B": ["C"], "D": [], "C": ["A"]}
>>> ts = TopologicalSorter(data)
>>> for a in ts.static_order():
...     print(a)
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/hughbrown/.pyenv/versions/3.12.0/lib/python3.12/graphlib.py", line 244, in static_order
    self.prepare()
  File "/Users/hughbrown/.pyenv/versions/3.12.0/lib/python3.12/graphlib.py", line 106, in prepare
    raise CycleError(f"nodes are in a cycle", cycle)
graphlib.CycleError: ('nodes are in a cycle', ['A', 'C', 'B', 'A'])
  
# This is a bit unexpected, given that E is not listed as a step that can be fulfilled.
>>> data = {"A": ["B", "D", "E"], "B": [], "D": [], "C": ["A"]}
>>> ts = TopologicalSorter(data)
>>> for a in ts.static_order():
...     print(a)
...
B
D
E
A
C