CODEWITHSUNDEEP
python
Tiger1
Tiger1

Reputation: 1377

How to identify an odd item in a list of items using python

My goal is to identify the odd element in the list below.

list_1=['taska1', 'taska2', 'taska3', 'taskb2', 'taska7']

The odd item is tasksb2 as the other four items are under taska.

They all have equal length, hence discriminating using the len function will not work. Any ideas? thanks.

Upvotes: 0

Views: 1163

Answers (3)

Caleb Hattingh
Caleb Hattingh

Reputation: 9245

If you know what the basic structure of the items will be, then it's easy.

If you don't know the structure of your items a priori, one approach is to score the items according to their similarity against each other. Using info from this question for the standard library module difflib,

import difflib
import itertools

list_1=['taska1', 'taska2', 'taska3', 'taskb2', 'taska7']

# Initialize a dict, keyed on the items, with 0.0 score to start
score = dict.fromkeys(list_1, 0.0)

# Arrange the items in pairs with each other
for w1, w2 in itertools.combinations(list_1, 2):
    # Performs the matching function - see difflib docs
    seq=difflib.SequenceMatcher(a=w1, b=w2)
    # increment the "match" score for each
    score[w1]+=seq.ratio()
    score[w2]+=seq.ratio()

# Print the results

>>> score
{'taska1': 3.166666666666667,
 'taska2': 3.3333333333333335,
 'taska3': 3.166666666666667,
 'taska7': 3.1666666666666665,
 'taskb2': 2.833333333333333}

It turns out that taskb2 has the lowest score!

Upvotes: 0

Mingyu
Mingyu

Reputation: 33379

If you simply want to find the item that does not start with 'taska', then you could use the following list comprehension:

>>> list_1=['taska1', 'taska2', 'taska3', 'taskb2', 'taska7']
>>> print [l for l in list_1 if not l.startswith('taska')]
['taskb2']

Another option is to use filter + lambda:

>>> filter(lambda l: not l.startswith('taska'), list_1)
['taskb2']

Upvotes: 3

Shashank
Shashank

Reputation: 13869

Seems to be an easy problem solved by alphabetical sort.

print sorted(list_1)[-1]

Don't wanna sort? Try an O(n) time-complexity solution with O(1) space complexity:

print max(list_1)

Upvotes: 1

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