I have a problem with "pairing" arrays into one (by index). Here is an example:
INPUT:
inputArray = [[0, 1, 2, 3, 4], [2, 3, 5, 7, 8], [9, 6, 1]]
EXPECTED OUTPUT:
outputArray =
[[0,2,9],
[1,3,6],
[2,5,1],
[3,7,chooseRandom()],
[4,8,chooseRandom()]]
Questions:
How to avoid "out of range" "index error" problem
How to write chooseRandom() to choose N neighbour
Answers:
[SOLVED] Solutions provided by #jonrsharpe & #Christian & #Decency works as
expected
Clarification:
By N neighbour I mean:
I'm using python but feel free to share your thoughts in any language.
I think the following will do what you want:
from itertools import izip_longest # 'zip_longest' in Python 3.x
from random import choice
# Step 1
outputArray = list(map(list, izip_longest(*inputArray)))
# Step 2
for index, arr in enumerate(outputArray):
if any(item is None for item in arr):
valid = [item for item in arr if item is not None]
outputArray[index] = [choice(valid) if item is None else item
for item in arr]
This has two steps:
Combine all sub-lists of inputArray to the length of the longest sub-array, filling with None: [[0, 2, 9], [1, 3, 6], [2, 5, 1], [3, 7, None], [4, 8, None]]; and
Work through the outputArray, finding any sub-lists that contain None and replacing the None with a random choice from the other items in the sub-list that aren't None.
Example output:
[[0, 2, 9], [1, 3, 6], [2, 5, 1], [3, 7, 3], [4, 8, 8]]
Here's my approach to the problem, in Python 3.4. I don't really know what you mean by "choose N neighbour" but it should be pretty easy to write that however you'd like in the context below.
inputArray = [[0, 1, 2, 3, 4], [2, 3, 5, 7, 8], [9, 6, 1]]
import itertools
zipped = itertools.zip_longest(*inputArray, fillvalue=None)
outputArray = [list(item) for item in zipped]
# [[0, 2, 9], [1, 3, 6], [2, 5, 1], [3, 7, None], [4, 8, None]]
# Now replace the sentinel None in our sublists
for sublist in outputArray:
for i, element in enumerate(sublist):
if element is None:
sublist[i] = chooseRandom()
print(outputArray)
Not the most pythonic way, but you could try using this code snipped, read the comments in the code below:
import itertools, random
inputArray = [ [0, 1, 2, 3, 4], [2, 3, 5, 7, 8], [9, 6, 1] ]
outputArray = []
max_length = max(len(e) for e in inputArray) # maximum length of the sublists in <inputArray>
i = 0 # to keep the index of sublists of <outputArray>
for j in range(max_length):
outputArray.append([]) # add new sublist
for e in inputArray: # iterate through each element of <inputArray>
try:
outputArray[i].append(e[j]) # try to append the number, if an exception is raised
# then the code in the <except> clause will be executed
except IndexError as e:
outputArray[i].append(random.randint(0, 10)) # add the random number
i += 1 # increase the sublists index on each iteration
print outputArray
# [[0, 2, 9], [1, 3, 6], [2, 5, 1], [3, 7, 3], [4, 8, 7]]
Note:
You may want to change the part
random.randint(0, 10)
to get the "N neighbour".
Let me know whether you like this code:
import random
array = [[0, 1, 2, 3, 4], [2, 3, 5, 7, 8], [9, 6, 1]]
max_len = max([len(l) for l in array])
dictionary = {}
for l in array:
for i in range(0,len(l)):
if dictionary.has_key(i):
dictionary[i].append(l[i])
else:
dictionary[i] = [l[i]]
for i in range(len(l),max_len):
if dictionary.has_key(i):
dictionary[i].append(random.choice(l))
else:
dictionary[i] = [random.choice(l)]
print dictionary.values()
Related
I was trying to extract lists from a tuple with a condition that every X numbers in ascending order should be extracted in same list, using a list comprehension.
Example:
Input: (4,2,2,3,5,6,0,0,2)
Desired output: [[4],[2,2,3,5,6],[0,0,2]]
I tried the following:
E=tuple([random.randint(0,10) for x in range(10)])
Res=[E[x:y] for x in range(0,len(E)) for y in range(x+1,len(E)) if (y>x)]
Here, simple logic to create new list already with the first element tuple. and then loop over tuple and if its current element is less then last element or not, if its smaller then append element as a list or append element into the last list.
Code:
import random
E=tuple([random.randint(0,10) for x in range(10)])
E
ls=[[E[0]]]
[ls.append([E[e]]) if E[e]<E[e-1] else ls[len(ls)-1].append(E[e]) for e in range(1, len(E)) ]
ls
OR Without pre-defining the first value
from itertools import pairwise
l=[[]]
[l[len(l)-1].append(y) if x-y < 0 else l.append([y]) for (x, y) in pairwise([e for e in (0,)+E])] ##Insert the dump 0 at first position
l
Input: (7, 10, 7, 2, 3, 7, 4, 3, 5, 10)
Output: [[7, 10], [7], [2, 3, 7], [4], [3, 5, 10]]
Input: (0, 3, 4, 3, 0, 7, 0, 0, 2, 3)
Output: [[0, 3, 4], [3], [0, 7], [0, 0, 2, 3]]
Here is one possible way to do this. You could use np.split together with random.sample to get the random numbers which is used as index to split.
import random
import numpy as np
lst = [4,2,2,3,5,6,0,0,2]
number_of_splits = 4
random.seed(42)
random_splits = sorted(random.sample(set(range(1,len(lst)-1)),number_of_splits-1))
print(random_splits)
result = [list(elem) for elem in np.split(lst, random_splits)]
print(result)
[1, 6, 7]
[[4], [2, 2, 3, 5, 6], [0], [0, 2]]
Probably easier to do this without a list comprehension - i.e., a straightforward loop like this:
from random import randint as RANDINT
t = 4, 2, 2, 3, 5, 6, 0, 0, 2
out = []
offset = 0
while offset < len(t):
e = RANDINT(1, len(t)+1-offset)
out.append(list(t[offset:offset+e]))
offset += e
print(out)
Output (example):
[[4], [2, 2], [3], [5, 6, 0, 0], [2]]
We can use slice to mark start and end of sub-lists
t=(4,2,2,3,5,6,0,0,2)
split_list=[0]+[x for x in range(len(t)) if t[x]<t[x-1]]
split_list_end=[x for x in range(len(t)) if t[x]<t[x-1]]
split_list_end.append(len(t))
[list(t[x]) for x in [slice(x[0],x[1]) for x in list(zip(split_list,split_list_end))]]
I'm new to python and i don't know how to find the smallest number in each array. The input is [ [2], [3, 4], [6, 5, 7], [4, 1, 8, 3] ] and the output should be [2, 3, 5, 1]. I have try this:
x = [ [2], [3, 4], [6, 5, 7], [4, 1, 8, 3] ]
minimal = x[0]
for i in range(len(x)):
if (x[i]< minimal):
minimal = x[i]
print(minimal)
And the output that i got is [2], i have no idea about this. Please help me...
We can simply iterate through the nested list and append the minimum values for each of the list item.
smallest = []
for listItem in x:
smallest.append(min(listItem))
Now, smallest list should be the expected output list.
First, we need to get individual lists from list x using for lst in x:. Then we find the minimum value of that list using min() function & append it to your minimal list using minimal.append(min(lst)), then print the final minimal list Now you will have your output as [2, 3, 5, 1]
Now try & understand this code:
x = [ [2], [3, 4], [6, 5, 7], [4, 1, 8, 3] ]
minimal = []
for lst in x:
minimal.append(min(lst))
print(minimal)
try this :
list(map(lambda x:min(x),[[2], [3, 4], [6, 5, 7], [4, 1, 8, 3] ]))
I have a list
a = [[1,2,3],[3,4,5]]
In every row at the end I want to insert values from a different list
b=[6,7]
I want the results to be
[[1,2,3,6],[3,4,5,7]]
I am using:
for i in range (0,len(a)):
for j in range (0,len(b)):
if j==0:
a[i].append(b[j])
m.append(a[i])
else:
a[i][3]=b[j]
m.append(a[i])
print m
But I am not getting the expected results. This gives me:
[[1, 2, 3, 7], [1, 2, 3, 7], [3, 4, 5, 7], [3, 4, 5, 7]]
Could someone help me out with the correct code snippet.
Here is a solution using zip:
result = [sublist_a + [el_b] for sublist_a, el_b in zip(a, b)]
which gives the expected output:
[[1, 2, 3, 6], [3, 4, 5, 7]]
Using zip
Ex:
a=[[1,2,3],[3,4,5]]
b=[6,7]
for i, j in zip(a,b):
i.append(j)
print(a)
Output:
[[1, 2, 3, 6], [3, 4, 5, 7]]
I have a list like [[1, 2, 4], [2, 5], [0, 3, 7, 8], [12, 3, 6], [18, 14]]. How can I get a list that contains lists of all the lists that contain overlapping elements added together? For the example input, the result should be [[1, 2, 4, 5], [0, 3, 6, 7, 8, 12], [14, 18]].
a = [[1, 2, 4], [2, 5], [0, 3, 7, 8], [12, 3, 6], [18, 14]]
result = []
for s in a:
s = set(s)
for t in result:
if t & s:
t.update(s)
break
else:
result.append(s)
This will go one-by-one through the list and create a set from the current sublist (s). Then it will check in the results, if there is another set t that has a non-empty intersection with it. If that’s the case, the items from s are added to that set t. If there is no t with a non-empty intersection, then s is a new independent result and can be appended to the result list.
A problem like this is also a good example for a fixed-point iteration. In this case, you would look at the list and continue to merge sublists as long as you could still find lists that overlap. You could implement this using itertools.combinations to look at pairs of sublists:
result = [set(x) for x in a] # start with the original list of sets
fixedPoint = False # whether we found a fixed point
while not fixedPoint:
fixedPoint = True
for x, y in combinations(result, 2): # search all pairs …
if x & y: # … for a non-empty intersection
x.update(y)
result.remove(y)
# since we have changed the result, we haven’t found the fixed point
fixedPoint = False
# abort this iteration
break
One way I can think of doing this is through recursion. Start with one item, then loop until you find every number it's connected to. For each of these numbers, you must do the same. Hence the recursion. To make it more efficient, store numbers you've visited in a list and check it at the beginning of each recursive sequence to make sure you don't repeat any explorations.
A two liner:
a_set = [set(x) for x in a]
result = [list(x.union(y)) for i,x in enumerate(a_set) for y in a_set[i:]
if x.intersection(y) and x != y]
I have left the last step for you:
a = [[1, 2, 4], [2, 5], [0, 3, 7, 8], [12, 3, 6], [18, 14]]
result = [[1, 2, 4, 5], [0, 3, 6, 7, 8, 12], [14, 18]]
# each sub list
result2 = []
count = 0
print a
for sub_list in a:
print count
print "sub_list: " + str(sub_list)
a.pop(count)
print "a: " + str(a)
#each int
sub_list_extend_flag = False
for int_in_sub_list in sub_list:
print "int_in_sub_list: " + str(int_in_sub_list)
for other_sub_list in a:
print "current_other_sub_list: " + str(other_sub_list)
if int_in_sub_list in other_sub_list:
sub_list_extend_flag = True
other_sub_list.extend(sub_list)
result2.append(list(set(other_sub_list)))
if not sub_list_extend_flag:
result2.append(sub_list)
count += 1
print result2
Simple answer:
a = [[1, 2, 4], [2, 5], [0, 3, 7, 8], [12, 3, 6], [18, 14]]
for x in a:
for y in x:
print y
its more simple than first one:
box=[]
a = [[1, 2, 4], [2, 5], [0, 3, 7, 8], [12, 3, 6], [18, 14]]
for x in a:
for y in x:
box.append(y)
print box
Result:[1, 2, 4, 2, 5, 0, 3, 7, 8, 12, 3, 6, 18, 14]
And with this, you can compare the numbers:
box=[]
box2=""
a = [[1, 2, 4], [2, 5], [0, 3, 7, 8], [12, 3, 6], [18, 14]]
for x in a:
for y in x:
box.append(y)
print box
for a in box:
box2+=str(a)
print box2
Result: 12425037812361814
Also you can make it more cute:
print " ".join(box2)
Result: 1 2 4 2 5 0 3 7 8 1 2 3 6 1 8 1 4
I have the following problem. Having a list of integers, I want to split it, into a list of lists, whenever the step between two elements of the original input list is not 1.
For example: input = [0, 1, 3, 5, 6, 7], output = [[0, 1], [3], [5, 6, 7]]
I wrote the following function, but it's uggly as hell, and I was wondering if anyone of you guys would help me get a nicer solution. I tried to use itertools, but couldn't solve it.
Here's my solution:
def _get_parts(list_of_indices):
lv = list_of_indices
tuples = zip(lv[:-1], lv[1:])
split_values = []
for i in tuples:
if i[1] - i[0] != 1:
split_values.append(i[1])
string = '/'.join([str(i) for i in lv])
substrings = []
for i in split_values:
part = string.split(str(i))
substrings.append(part[0])
string = string.lstrip(part[0])
substrings.append(string)
result = []
for i in substrings:
i = i.rstrip('/')
result.append([int(n) for n in i.split('/')])
return result
Thanks a lot!
This works with any iterable
>>> from itertools import groupby, count
>>> inp = [0, 1, 3, 5, 6, 7]
>>> [list(g) for k, g in groupby(inp, key=lambda i,j=count(): i-next(j))]
[[0, 1], [3], [5, 6, 7]]
def _get_parts(i, step=1):
o = []
for x in i:
if o and o[-1] and x - step == o[-1][-1]:
o[-1].append(x)
else:
o.append([x])
return o
_get_parts([0, 1, 3, 5, 6, 7], step=1)
# [[0, 1], [3], [5, 6, 7]])
Here is a solution utilizing a for loop.
def splitbystep(alist):
newlist = [[alist[0]]]
for i in range(1,len(alist)):
if alist[i] - alist[i-1] == 1:
newlist[-1].append(alist[i])
else:
newlist.append([alist[i]])
return newlist
This is how I'd do it:
inp = [0, 1, 3, 5, 6, 7]
base = []
for item in inp:
if not base or item - base[-1][-1] != 1: # If base is empty (first item) or diff isn't 1
base.append([item]) # Append a new list containing just one item
else:
base[-1].append(item) # Otherwise, add current item to the last stored list in base
print base # => [[0, 1], [3], [5, 6, 7]]
This is the textbook use case for function split_when from module more_itertools:
import more_itertools
print(list(more_itertools.split_when([0, 1, 3, 5, 6, 7], lambda x,y: y-x != 1)))
# [[0, 1], [3], [5, 6, 7]]
Or, even more simple with more_itertools.consecutive_groups:
print([list(g) for g in more_itertools.consecutive_groups([0, 1, 3, 5, 6, 7])])
# [[0, 1], [3], [5, 6, 7]]