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Python Data Type Q&A » List » algorithm 

1. Getting the lesser n elements of a list in Python    stackoverflow.com

I need to get the lesser n numbers of a list in Python. I need this to be really fast because it's in a critical part for performance and it needs ...

2. Algorithm to keep a list of percentages to add up to 100%    stackoverflow.com

(code examples are python)
Lets assume we have a list of percentages that add up to 100:

mylist = [2.0, 7.0, 12.0, 35.0, 21.0, 23.0]
Some values of mylist may ...

3. Python: For each list element apply a function across the list    stackoverflow.com

Given [1,2,3,4,5], how can i do something like 1/1, 1/2, 1/3,1/4,1/5, ...., 3/1,3/2,3/3,3/4,3/5,.... 5/1,5/2,5/3,5/4,5/5 I would like to store all the results, find the minimum, and return the two numbers used to ...

4. Splitting up a list into parts of balanced lengths    stackoverflow.com

I need an algorithm which given a list L and a number N, returns a list of N smaller lists where the sublists are "balanced". Examples:

algo(range(1, 8), 3)  -> ...

5. Python program to split a list into two lists with alternating elements    stackoverflow.com

Can you make it more simple/elegant?

def zigzag(seq):
    """Return two sequences with alternating elements from `seq`"""
    x, y = [], []
    p, q ...

6. An ALGORITHM to create one list from "X" nested lists in Python    stackoverflow.com

What is the simplest way to create this list in Python? First, suppose I have this nested list:

oldList = [ [{'letter':'a'}], [{'letter':'b'}], [{'letter':'c'}] ]
I want a function to spit out:
newList = [ ...

7. algorithm for list identification and parsing    stackoverflow.com

I have data which in theory is a list, but historically has been input by the user as a free form text field. Now I need to separate each item of ...

8. How can I sort a coordinate list for a rectangle counterclockwise?    stackoverflow.com

I need to sort a coordinate list for a rectangle counterclockwise, and make the north-east corner the first coordinate. These are geographic coordinates (i.e. Longitude, Latitude) in decimal form.1 For example, here ...

9. Python - Simple algorithmic task on lists (standard question for a job-interview)    stackoverflow.com

There are 2 input lists L and M, for example:

L =  ['a',     'ab',  'bba']
M = ['baa', 'aa',  'bb']
How to obtain 2 non-empty output lists ...

10. Pythonic way of summing lists and lists of lists    stackoverflow.com

I'm trying to find a neat way of summing a list and a list of lists in the same function, so far I've got:

import operator
"""
 Fails late for item = ['a', ...

11. Python: Get items at depth? (set library?)    stackoverflow.com

I have a nested list something like this:

PLACES = (
    ('CA', 'Canada', (
        ('AB', 'Alberta'),
       ...

12. Take the intersection of an arbitrary number of lists in python    stackoverflow.com

Suppose I have a list of lists of elements which are all the same (i'll use ints in this example)

[range(100)[::4], range(100)[::3], range(100)[::2], range(100)[::1]]
What would be a nice and/or efficient way to ...

13. Show me some cool python list comprehensions    stackoverflow.com

One of the major strengths of python and a few other (functional) programming languages are the list comprehension. They allow programmers to write complex expressions in 1 line. ...

14. Optimize algorithm for creating a list of items rated together, in Python    stackoverflow.com

given a list of purchase events (customer_id,item)

1-hammer
1-screwdriver
1-nails
2-hammer
2-nails
3-screws
3-screwdriver
4-nails
4-screws
i'm trying to build a data structure that tells how many times an item was bought with another item. Not bought at the same time, ...

15. Determining the minimum of a list of n elements    stackoverflow.com

I'm having some trouble developing an algorithm to determine the minimum of a list of n elements. It's not the case of finding the minimum of an array of length n, ...

16. overlapping segments    stackoverflow.com

i have a huge list of two-element tuples which are coordinates of segments (start, end). In this way in a list below

list = [ (1,4), (2, 3), (10, 20), (18, 45) ...

17. I have a Python list of the prime factors of a number. How do I (pythonically) find all the factors?    stackoverflow.com

I'm working on a Project Euler problem which requires factorization of an integer. I can come up with a list of all of the primes that are the factor of a ...

18. Lowest common multiple for all pairs in a list    stackoverflow.com

I have some code that calculates the lowest common multiple for a list of numbers. I would like to modify this code to return a list of values that represents ...

19. Pythonic way to check if a list is sorted or not    stackoverflow.com

Is there a pythonic way to check if a list is already sorted in AESC or DESC. listtimestamps=[1,2,3,5,6,7] something like listtimestamps.isSorted() that returns True or False. EDIT: I want to input a list of ...

20. Sort distributed couples from two lists    stackoverflow.com

Having two lists, I want to get all the possible couples. (a couple can be only one element from list 1 and another from list 2) If I do a double "foreach" ...

21. Determine if a Python list is 95% the same?    stackoverflow.com

This question asks how to determine if every element in a list is the same. How would I go about determining if 95% of the elements in a list ...

22. How to get the smallest list of duplicate items from list of lists?    stackoverflow.com

I'm a Python newbie, I worked with list for 2 months and I have some questions. I have some list and they have duplicate items. I can get duplicate items between ...

23. Fast algorithm to calculate delta of two list    stackoverflow.com

I have two list of album names, ordered by some score.

albums_today = ['album1', 'album2', 'album3']
albums_yesterday = ['album2', 'album1', 'album3']
How can I calculate the change of list order and get something like
{'album1':1, ...

24. List of minimal pairs from a pair of lists    stackoverflow.com

Given two lists of integers, generate the shortest list of pairs where every value in both lists is present. The first of each pair must be a value from the first ...

25. Python Sort List    stackoverflow.com

I'm currently python and quite new to this language. Sort List Based on Two CriteriaGiven a list of words, return a list with the same words in order of length (longest to ...

26. efficient comparison of values in a python list    stackoverflow.com

I have a list made out of tuples such as the one below:

(2809.3994479562093, 1032.5989696312365, 0.0), {'level': '2', 'id': '1'})
having a sett of different values for the level key in the ...

27. Python Lists - How this connection is made?    stackoverflow.com

I'm reading about algorithms in Python but I'm also new in Python. I just need to understand how this is made:

a, b, c, d, e, f, g, h = range(8)
N = [
[b, ...

28. How to partition a list in smaller lists so that the odds of one element encountering another element is evenly distributed?    stackoverflow.com

I'm struggling with an algorithm to divide a group of contestants into smaller groups to make up rounds. Take for example a group of 20 people, which I want to divide ...

29. Calculating the similarity of two lists    stackoverflow.com

I have two lists: eg. a = [1,8,3,9,4,9,3,8,1,2,3] and b = [1,8,1,3,9,4,9,3,8,1,2,3] Both contain ints. There is no meaning behind the ints (eg. 1 is not 'closer' to 3 than it is to 8). I'm trying ...

30. splitting list in chunks of balanced weight    stackoverflow.com

I need an algorithm to split a list of values into such chunks, that sum of values in every chunk is (approximately) equals (its some variation of Knapsack problem, ...

31. partition of a list using dynamic programming    stackoverflow.com

I have posted a bit here related to a project I have been trying to work on and I keep hitting design problems and have to design from scratch. So ...

32. How to pick the largest number in a matrix of lists in python?    stackoverflow.com

I have a list-of-list-of-lists, where the first two act as a "matrix", where I can access the third list as

list3 = m[x][y]   
and the third list ...

33. The best way recognizing similarity of list lengths    stackoverflow.com

I have a dict containing lists under its keys:

dct = {'a': [1, 2, 3],
       'b': [1, 2, 3, 4],
       ...

34. How to efficiently compare two unordered lists (not sets) in Python?    stackoverflow.com

a = [1, 2, 3, 1, 2, 3]
b = [3, 2, 1, 3, 2, 1]
a & b should be considered equal, because they have exactly the same elements, only in different ...

35. Pascal's Triangle with iterative algorithm via list comprehension in Python    stackoverflow.com

Just for the sake of exercise I'm trying to find a way to express Pascal's Triangle with Python list comprehension, and do that in iterative way. I'm representing Pascal's ...

36. pythonic way to sort a list of lists by the last item of the inner list    stackoverflow.com

I have a list like this

[[x,y,1],[w,u,4],[m,n,3] ... [p,q,5]]
I need to sort the outer list by the third (last) element of the inner list, the desired result would be:
[[x,y,1],[m,n,3],[w,u,4] ... [p,q,5]]
What's the ...

37. Python topological sort using lists indicating edges    stackoverflow.com

Given lists: [1, 5, 6], [2, 3, 5, 6], [2, 5] etc. (not necessarily in any sorted order) such that if x precedes y in one list, then x precedes ...

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