Iterate through list in nested list

I have a long list with nested lists with each list consisting of multiple xy-coordinates. In short, my lists looks like this

MyList = [ [ [1, 2], [1, 2] ], [ [1, 2], [1, 2] ], [ [1, 2], [1, 2] ]...]]]

I would like to extract all the "1's" to one variable, and all the "2's" to one variable. So extract first element to a new list, and extract second element to another new list. I have tried

for list in MyList:
   for newList in list:
      number1 = [item[0] for item in newList]
      number2 = [item[1] for item in newList]

Which gave me the error "int object is not subscriptable". I also tried

def Extract(MyList):
   return list(list(zip(*MyList))[0])

Lastly I tried to just print the "1's" out to see if it would work

print(MyList[:][:][0])
output: [[1, 2], [1, 2]]

CodePudding user response：

I would do it like so:

>>> a = MyList
>>> x = [a[i][j][0] for i in range(len(a)) for j in range(len(a[i]))]
>>> x
[1, 1, 1, 1, 1, 1]
>>> y = [a[i][j][1] for i in range(len(a)) for j in range(len(a[i]))]
>>> y
[2, 2, 2, 2, 2, 2]

You're basically iterating over each tuple of coordinates and take the X coordinate ([0]), respectively the y coordinate ([1]).

There might be better ways, this is the quick one I came up with.

CodePudding user response：

Try this:

flatlist = [el for lst1 in MyList for lst2 in lst1 for el in lst2]
number1, number2 = flatlist[0::2], flatlist[1::2]

First you flat the list, and then you split it into two lists with alternating elements.

CodePudding user response：

Simply you can handle this with three for loop if time complexity is not an issue:

one = []
two = []
for item in MyList:
   for arr in item:
      for num in arr:
         if num == 1:
            one.append(num)
         else:
            two.append(num) 

# [1, 1, 1, 1, 1, 1]
# [2, 2, 2, 2, 2, 2]