Check if items in list alternatingly match keys in two dicts

alternatingtest.py

# fake YAML input data (only keys matter)
connectors = {'A': [1,2,3], 'B': [1,2,4], 'C': [3,6,7]}
cables     = {'X': [4,4,4], 'Y': [4,5,6], 'Z': [9,9,9]}

# list to check, should alternatingly contain connector and cable keys, may start with either
listy = ['A','X','B','Y','C']

conkeys = list(connectors.keys())
cblkeys = list(cables.keys())

print('conkeys', conkeys)
print('cblkeys', cblkeys)

found_in_con = [item in conkeys for item in listy] # should contain alternating True and False
found_in_cbl = [item in cblkeys for item in listy] # should contain alternating False and True (reversed)

print('found_in_con', found_in_con)
print('found_in_cbl', found_in_cbl)

alternating = ([True, False] * ((len(listy)+1) // 2))[0:len(listy)] # generate alternating True and False list, with length = len(listy)

check1 = [item == check for (item, check) in zip(found_in_con, alternating)] # should contain all True if list starts with connector, all False if list starts with cable, both True and False if it does not alternate properly
check2 = [item != check for (item, check) in zip(found_in_con, alternating)] # same as above, but with inverted logic

print('check1', check1)
print('check2', check2)

starts_with_connector = all(check1) and not any(check2)
starts_with_cable     = all(check2) and not any(check1)

OK = starts_with_connector or starts_with_cable

print('OK?', OK)

One drawback with the approach to test all items together by comparing lists, is that it might not be so easy to report the first item that is unexpected. A simple naive approach is to test the first item for all alternatives, and then in a loop, test for alternating item is connector or cable/wire. Then the first unexpected value is easy to report. As a user, I would prefer a report on the first unecpected value together with a description of what was expected.

Very good point!

See one alternative in my fork:
https://gist.github.com/kvid/5c4c0f65111b4c4569b2be875541e7c1

I like it! I'll build on that. Thanks!