python 3 comprehension dictionary

Question

This is my code:

def brujinGraph(k, strList):

    vertex = [[0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0], [0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0], [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0]]

    brujinGraph = {strList[i]: strList[j][:-1] for i in range(len(vertex)) for j in range(k) and vertex[i][j] == 1}

    return brujinGraph

strList = ['AAGA', 'AAGA', 'AGAT', 'ATTC', 'CTAA', 'CTCT', 'GATT', 'TAAG', 'TCTA', 'TCTC', 'TTCT']
brujinGraph(4, strList)

and it is throwing me an UnboundLocalError: local variable 'j' referenced before assignment

any idea what does it means and why am I getting this error?

Possible duplicate of [Create a dictionary with list comprehension in Python](http://stackoverflow.com/questions/1747817/create-a-dictionary-with-list-comprehension-in-python) — Jason, Mar 13 '16 at 01:06
Please show us the rest of your code so we can reproduce it. To me it looks like your trying to reference a key `j` in `strList`(assuming `strList` is a dict) when j doesnt exist in `strList`. — Jason, Mar 13 '16 at 01:08
The second range will be evaluated before the `for j`, and the range depends on `j`. That just won't work. — Joachim Isaksson, Mar 13 '16 at 01:10
@JoachimIsaksson I get same error even if I change the second range with a contant — masber, Mar 13 '16 at 01:25
Could you explain what your desired output is? There are multiple oddities in the comprehension so I can't quite figure out what needs to be changed to get the result you're looking for. — Joachim Isaksson, Mar 13 '16 at 07:35

score 1 · Accepted Answer · answered Mar 13 '16 at 01:18

1

Without knowing exactly what vertex and strList are :

Do you actually mean :

{strList[i]: strList[j][:-1] for i in range(len(vertex)) for j in range(len(vertex[i])) if vertex[i][j] == 1}

i.e. change that and into an if

answered Mar 13 '16 at 01:18

Tony Suffolk 66

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score 1 · Answer 2 · edited Jun 20 '20 at 09:12

1

Couple of issues:

You need an if not an and at the end
I think it is better expressed this way:

brujinGraph = {strList[i]: strList[j][:-1] for i, x in enumerate(vertex) for j, e in enumerate(x) if e == 1}

edited Jun 20 '20 at 09:12

Community

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answered Mar 13 '16 at 01:42

dawg

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python 3 comprehension dictionary

2 Answers2