CODEWITHSUNDEEP
pythonlistloopsappend
Price Nimmich
Price Nimmich

Reputation: 39

Searching for Equivalence Among Elements of a List

I have the following code in place

Trans_Func = [['s1', '@', 's2'], ['s1', '@', 's4'], ['s2', '0', 's2'], ['s2', '1', 's3'], ['s3', '0', 's3'], ['s3', '1', 's3'], ['s3', '2', 's3'], ['s4', '1', 's4'], ['s4', '2', 's4'], ['s4', '2', 's5']]
new_rules = []
for i, j in Trans_Func:
    if i[0] == j[0] and i[1] == j[1]:
        #operation to append the new rule
print(new_rules)

I am trying to create a new list that contains elements from Trans_Func only when the first strings are equivalent, the second strings are equivalent, but the third strings are different. My expected output for new_rules is:

new_rules = [['s1', '@', 's1, s4'], ['s4', '2', 's4, s5']]

I just do not know how to loop through Trans_Func in an attempt to inspect multiple elements at the same time.

Upvotes: 0

Views: 59

Answers (3)

Alain T.
Alain T.

Reputation: 42143

You can use a dictionary to manage matching pairs as keys and accumulate the 3rd strings in a list as the values. Then run through the dictionary to isolate pairs that have more than one associated 3rd string:

d = dict()
for s1,s2,s3 in Trans_Func: d.setdefault((s1,s2),[]).append(s3)
new_rules = [ [s1,s2,", ".join(ss)] for (s1,s2),ss in d.items() if len(ss)>1 ]

print(new_rules)
[['s1', '@', 's2, s4'], ['s4', '2', 's4, s5']]

Upvotes: 1

Syed
Syed

Reputation: 146

Here you go

for i in range(len(Trans_Func)):
    IF i<len(Trans_Func)-1:
        if Trans_Func[i][1]==Trans_Func[i+1][1] and Trans_Func[i][2]==Trans_Func[i+1][2]:
            #operation to append the new rule

Upvotes: 1

RomanPerekhrest
RomanPerekhrest

Reputation: 92854

Give your variables a proper names (lowercase and meaningful), say trans_list (for ex.).
With effective generator expression and zip function:

trans_list = [['s1', '@', 's2'], ['s1', '@', 's4'], ['s2', '0', 's2'], ['s2', '1', 's3'], ['s3', '0', 's3'],
              ['s3', '1', 's3'], ['s3', '2', 's3'], ['s4', '1', 's4'], ['s4', '2', 's4'], ['s4', '2', 's5']]
new_rules = list([lst_1[0], lst_1[1], lst_1[2] + ', ' + lst_2[2]]
                 for lst_1, lst_2 in zip(trans_list[:-1], trans_list[1:])
                 if lst_1[:2] == lst_2[:2] and lst_1[2] != lst_2[2])
print(new_rules)

The output:

[['s1', '@', 's2, s4'], ['s4', '2', 's4, s5']]

Upvotes: 0

Related Questions