遍历嵌套列表中的列表 - Python

Question

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]]

Answer 1

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.

Answer 2

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.

Answer 3

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]