Select random items from list of lists in Python

Question

I have a list of lists of different lengths. From each list of lists, I need to randomly select 10 items. Then I have to combine the results in a single list with each list item separated by comma. (Pls see the output below). Not sure whether this is possible in Python. Any help would be appreciated.

[[-26.0490761  27.79991  ]
 [-25.9444218  27.9116535]
 [-26.1055737  27.7756424]
 ..., 
 [-26.036684   28.0508919]
 [-26.1367035  28.2753029]
 [-26.0668163  28.1137161]]

[[ 45.35693   -63.1701241]
 [ 44.6566162 -63.5969276]
 [ 44.7197456 -63.48137  ]
  ..., 
 [ 44.624588  -63.6244736]
 [ 44.6563835 -63.679512 ]
 [ 44.66706   -63.621582 ]]

I would like to get the output in this format that is suitable for plotting them on a map using Folium.

 [[-26.0490761  27.79991],
  [-25.9444218  27.9116535],
  [ 44.6563835 -63.679512 ],
  [ 44.66706   -63.621582 ]]

I tried this code but not sure what went wrong:

  for cluster in clusters:
    for i in range(2):
       modifiedlist.append(cluster)

John Coleman · Accepted Answer · 2016-11-17 17:41:25Z

2

Something like this is easy using the module random:

import random

def sampleFromLists(lists,n):
    """draws n elements from each list in lists
returning the result as a single list"""
    sample = []
    for subList in lists:
        sample.extend(random.sample(subList,n))
    return sample

Sample data (a list of lists of 2-element lists):

data = [
    [[-26.0490761, 27.79991],
     [-25.9444218, 27.9116535],
     [-26.1055737, 27.7756424],
     [-26.036684, 28.0508919],
     [-26.1367035, 28.2753029],
     [-26.0668163,28.1137161]],

    [[ 45.35693, -63.1701241],
     [44.6566162 -63.5969276],
     [44.7197456, -63.48137],
     [44.624588, -63.6244736],
     [44.6563835,-63.679512],
     [44.66706, -63.621582]]
]

And then:

>>> sampleFromLists(data,2)
[[-26.036684, 28.0508919], [-26.0490761, 27.79991], [44.7197456, -63.48137], [44.6563835, -63.679512]]

edited Nov 17, 2016 at 17:41

answered Nov 17, 2016 at 16:34

John Coleman

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4 Comments

user3447653 Over a year ago

Thanks for your response. But When we pass in [[1,2,3,4],[5,6,7,8],[9,10,11,12]] and select 2 numbers randomly from each list, the output has to be [[2,3][5,6],[9,12]] (random 2 elements from each list).

John Coleman Over a year ago

Just replace extend by append in the above code if you need. Note that your data seems to be of a list of list of 2-element lists, so I think that if you run my code with your data (assuming that it is all just one big list of lists) then the output will be a list of 2-element lists. Thus, unless I misunderstood your set up, I think that my code should work as is.

John Coleman Over a year ago

@user3447653 the edit shows what I mean -- I made the sample reflect the data in your question.

Sca Over a year ago

[['p1', 'p2', 'p3', 'p4', 'p5'], ['p6', 'p7', 'p8', 'p9', 'p10'], ['p11', 'p12', 'p13', 'p14', 'p15'], ['p16', 'p17', 'p18', 'p19', 'p20']] I have list like this... how do i modify the above code to get me output like : [p2,p9,p12,p19]? randomly choosing one element from a sublist and printing out the list?

MooingRawr · Accepted Answer · 2016-11-17 16:43:43Z

0

import random

x = [[1,2],[3,4],[5,6],[7,8],[9],[7675,6456,4],[5,6]]

z = []
for i in range(10):
  y = random.choice(x)
  z.append([random.choice(y), random.choice(y)])

print(z)

random.choice() picks a random item from the given input (in our case a list).

answered Nov 17, 2016 at 16:43

MooingRawr

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