Develop Reference

Random Question Sequence From Array Python [closed]

Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 2 years ago.
Improve this question
I have 5 arrays with 6 questions in each one.
I need the script to pick 2 questions from each array and create an input() function. The part I can't seem to think of is how to make an output for a correct answer for the questions. I understand how a specified input would work but what about randomized.

I think you're looking for something like this:
randomNumber1=***some generated number (0 thru 6)
randomNumber2=***some generated number (0 thru 6)
array1=['what is the meaning of life', 'how far away is the sun',...]
array2=['what did is your favorite color', 'how many pennies are in 1 dollar'...]
q1=array1[randomNumber1]
q2=array2[randomNumber2]
input1=input(q1)
input2=input(q2)
#stores answers in a dictionary
answers={q1:input1, q2:input2}

I do not think the random module has the function that you want.
But it is easy to build one if you like. Python is easy.
Does this work?
import random
from typing import Iterable
def get_sub_random_list(sub_length: int, iterable: Iterable) -> list:
iterable_copy = list(iterable)
result = []
for __ in range(sub_length):
length = len(iterable_copy)
if length == 0:
raise ValueError(f"the iterable should longer than {sub_length}")
index = random.choice(range(length))
result.append(iterable_copy[index])
del iterable_copy[index]
return result
example:
>>> get_sub_random_list(1, [1, 2, 3, 4, 5, 6])
[5]
>>> get_sub_random_list(6, [1, 2, 3, 4, 5, 6])
[4, 1, 5, 2, 6, 3]
The complexity is O(n+m): n is the length of iterable, and the m is the the times of the loop.

If i've scrambled an array, `a`, to get an array `b`, how can I get an array of indices, '`i` such that `b[i] == a`? [closed]

Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 2 years ago.
Improve this question
I know in both MATLAB and numpy in Python, you can return the indices that were used to sort an array a to get a sorted array, b. I'm asking for the general algorithm implementation behind returning these indices when you're not sorting, but simply scrambling. This must be a known algorithm, but I didn't know what to look for when searching for this.
E.g. say I have an array a == [7,6,8,9], and I set b=a[3,4,2,1] so b == [8,9,6,7]. Given this information, what is the most efficient code that would take me back from b to a (i.e. code that would yield the array i = [4,3,1,2], because b[i] == a). This should be applicable to an array of any size. I'm asking for an explanation and code in either MATLAB or Python, thanks!

In Matlab, just use the second output of sort:
ind = [3,4,2,1];
[~, result] = sort(ind);
Or, as suggested by #CrisLuengo, you can do it just with indexing:
result(ind) = 1:numel(ind);
Either of the above gives
result =
4 3 1 2

Python Code :
a = [7, 6, 8, 9, 8]
b = [8, 8, 9, 7, 6]
i = []
for x in a:
index = b.index(x)
i.append(index)
# for duplicates
b[index] = -1
print(i)
Output :
[3, 4, 0, 2, 1]

How to remove double [] from a list? [closed]

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 2 years ago.
Improve this question
I have a list like this:
my_lst = [[1,2,3,4]]
I was wondering how can I remove [] from the list to get the following list:
my_lst = [1,2,3,4]

The double [[]] is because you have a list containing a list. To get out the inner list, just index it:
my_lst = my_lst[0]
or unpack it:
[my_lst] = my_lst
Unpacking has the mild advantage that it will give you an error if the outer list doesn't not contain exactly one value (while my_lst[0] will silently discard any extra values).
There are many other options.

my_lst = my_lst[0]
You have a list with one element, which is itself a list. You want the variable to just be that first element, the list 1,2,3,4.

you have a list of lists.
my_lst = my_lst[0] #get the first list of the list

You can use itertools to achieve that without writing your explicit loop if the length of the outer list could be more than one.
In [47]: import itertools
In [49]: list(itertools.chain.from_iterable([[1, 2, 3], [1, 2]]))
Out[49]: [1, 2, 3, 1, 2]

You can reduce 1 dimension using sum.
my_lst=sum(my_lst,[])
# [1,2,3,4]

find all nested array in single array in python WITHOUT FLATTEN or any inbuilt function [closed]

Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 3 years ago.
Improve this question
Hi I need a single list of nested lists in python without any inbuilt function. I did a lot of research but not able to find without flatten or ravel function().
for ex:
input = [1,2,[2,3,[4,5]],[6,7],[8,[9]],10]
output = [1,2,2,3,4,5,6,7,8,9,10]

You can use recursion to implement your own flatten function. Here's a nice tutorial explaining the concepts of recursion.
The idea here is that you loop through each element in your list and if you encounter a sublist you recursively call the same method with the current list. If it's a valid element you add it to to your output list.
Example:
def flatten(input_list, output_list=[]):
for i in input_list:
if isinstance(i, list):
flatten(i, output_list)
else:
output_list.append(i)
return output_list
input_list = [1,2,[2,3,[4,5]],[6,7],[8,[9]],10]
print(flatten(input_list))
Outputs:
[1, 2, 2, 3, 4, 5, 6, 7, 8, 9, 10]

I found a solution on my own. Below is the solution:
c = []
def test(a):
for val in a:
if type(val) == list:
test(val)
else:
c.append(val)
return c
a=[1,2,[2,3,[4,5]],[6,7],[8,[9]],10]
print test(a)

Python: The Replacements [closed]

Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 7 years ago.
Improve this question
I'm currently trying to complete Computer Science Circles online but I am stuck on part 14: Methods. Here is the question.
Using index and other list methods, write a function replace(list, X, Y) which replaces all occurrences of X in list with Y. For example, if L = [3, 1, 4, 1, 5, 9] then replace(L, 1, 7) would change the contents of L to [3, 7, 4, 7, 5, 9]. To make this exercise a challenge, you are not allowed to use [].
Note: you don't need to use return.
I would probably be able to do this if we were allowed to use square brackets.
Here is what I have so far.
def replace(L, X, Y):
while X in L:
var = L.index(X)
var = Y
return(L)

I'll give some tips since this is an exercise.
1) You already found out the index where you're supposed to replace one element with another. What other way is there to replace a value in a given index? Check all the methods of list.
2) A list comprehension also allows an elegant solution:
[...???... for value in list]
You'll need to figure out what the expression should be, and how to make the comprehension modify your original list, not just create a new one.