nested for loop not counting correctly (python)

August 4, 2022

I have two lists:

common_nodes_list = ['A', 'A', 'B', 'C', 'C', 'C']
uniquePatterns = ['A', 'B', 'C']

I am trying to create a dict with the counts of each unique pattern. Like this:

A: 2
B: 1
C: 3

I have a for loop inside of another for loop:

patternRank = {}

for i in common_nodes_list:
    score = 0
    for pattern in uniquePatterns:
        if pattern == i:
            score += 1   
    patternRank[pattern]=score

patternRank

but It’s only returning:

'C': 1

>Solution :

You should do it the other way: for each pattern in the unique patterns, count how many there are in the common_nodes_list:

common_nodes_list = ['A', 'A', 'B', 'C', 'C', 'C']
unique_patterns = ['A', 'B', 'C']

pattern_rank = {}

for pattern in unique_patterns:
    score = 0
    for node in common_nodes_list:
        if node == pattern:
            score += 1
    pattern_rank[pattern] = score

print(pattern_rank)
>> {'A': 2, 'B': 1, 'C': 3}

And maybe, try to be consistant with the way you name the variables: snake_case or CapWords.