CODEWITHSUNDEEP
pythonlistsortinglinked-list
Marcus Sandri
Marcus Sandri

Reputation: 65

Error when search values in Python

I have a linked list with the following values:

switch_list = [[4, 1, 2, 2],
               [4, 2, 3, 2],
               [3, 1, 1, 3],
               [3, 2, 4, 2],
               [1, 3, 3, 1],
               [1, 2, 2, 1], 
               [2, 1, 1, 2],
               [2, 2, 4, 1]]

My goal is to compare an integer with the first value of the all linked-list and then, return a new list with filtered values.

Example: I want all values in switch_list with the first number equals 4, then the function will returns: 

[[4, 1, 2, 2], [4, 2, 3, 2],]

Here is my program:

def bucket(value, input): 

    output = []

    for i in input:
        if i[0][0] == value:
            output.append(i)

    return output

And here is the output error:

File "matrix_optimizate.py", line 63, in bucket
  if i[0][0] == value:
TypeError: 'int' object has no attribute '__getitem__'

Upvotes: 1

Views: 55

Answers (2)

Iman K
Iman K

Reputation: 357

I am assuming that input is going to be your list of lists. In that case,

for i in input:

will give you each sub list as i during each iteration. By trying to access

i[0][0]

you are trying to access the first element of the element of the sublist. In your example

  • i would give [4, 1, 2, 2]
  • i[0] would give 4, and
  • i[0][0] would therefore not make sense

Please try i[0] instead.

Edit: Please note that this answer only serves to point out your current problem. dursk's answer provides other solutions to what you are trying to perform as a whole and those options are much more powerful (list comprehension is a fantastic tool, I would recommend looking into it).

Upvotes: 3

dursk
dursk

Reputation: 4445

You're already iterating over the outer list, so there's no need for two index lookups.

for i in input:
    if i[0] == value:
        output.append(i)

Also, there's a much more elegant way to do this using filter:

def bucket(input, value):
    return filter(lambda x: x[0] == value, input)

At which point you probably don't even need to have it as it's own function.

And lastly you could use a list comprehension as well:

[i for i in input if i[0] == value]

Upvotes: 3

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