how to sort a list in python by two arguments

Question

I'm making a project about handwriting recognition so i have picture i have to recognize the text in it so what i did is that I made all the characters in the picture an objects (contour) ,the problem is that after printing the characters its printed unsorted(or by the x or by the y), and what i need is to sort a list full object from the top left to the bottom right.

I have tried to sorted by the y coordinates and then by x coordinates it will be sorted as an x coordinates from the beginning.

a.sort(key = operator.attrgetter("intRectx"))     
a.sort(key = operator.attrgetter("intRectY"))

I expect the project will print the characters as they written.

class Data():
 num1 = None           
 num2 = None        
 intRectX = 0                # x
 intRectY = 0                # y
 num3 = 0            
 num4 = 0        
 num5 = 0.0             

a = []                                                       # we will fill these shortly
for Data in all:                                    # for all contours
    if Data.checkIfContourIsValid():              # check if valid
        a.append(Data)                            # if so, append to valid contour list
a.sort(key = lambda x: (x.intRectY, x.intRectx))

Primusa · Answer 1 · 2019-01-16T20:23:18.987

2

Sort with a lambda expression that returns a tuple:

a.sort(key = lambda x: (x.intRectx, x.intRectY))

Edit:

If you want to sort by y then the x swap the order:

a.sort(key = lambda x: (x.intRectY, x.intRectx))

edited Jan 16 '19 at 20:23

answered Jan 16 '19 at 20:12

Primusa

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i have tried it but i got an error saying:"TypeError: 'a' object is not subscriptable" – Dean Amir Jan 16 '19 at 20:16
@DeanAmir ah i made a silly mistake, try now – Primusa Jan 16 '19 at 20:17
Make sure that `intRectx` and `intRectY` are the correct attributes if you get an `AttributeError` – Primusa Jan 16 '19 at 20:19
the error is gone but it still being sorted by the X coordinates – Dean Amir Jan 16 '19 at 20:21
@DeanAmir It should be `a.sort(key = lambda x: (x.intRectY, x.intRectx))` – mad_ Jan 16 '19 at 20:23
@DeanAmir see edit – Primusa Jan 16 '19 at 20:23
@Primusa see edit – Dean Amir Jan 16 '19 at 20:45
but what is the problem? is it still not sorting to your specifications? – Primusa Jan 16 '19 at 20:46
it didn't sorted how i want it – Dean Amir Jan 16 '19 at 20:47
You said you wanted top left to bottom right. Under the assumption that your x axis is horizontal and your y axis is vertical, this sorts from the top left to bottom right – Primusa Jan 16 '19 at 20:48
Can you give an example of your intended input / output? – Primusa Jan 16 '19 at 20:50
>a = [0.25,1.67 ], [0.8, 189], [1.2, 2], [1.3, 1.75],[1.9, 2.1],[2,1.4] >output = [1.9, 2.1],[2,1.4],[1.2, 2],[1.3, 1.75], [0.8, 189],[0.25,1.67 ] – Dean Amir Jan 16 '19 at 20:56
is that the input or the output? Because if that's the output you're sorting by the x coordinates, which is what my answer was in the beginning... – Primusa Jan 16 '19 at 20:56
i need to sort this...by somehow – Dean Amir Jan 16 '19 at 21:00
try `a.sort(key = lambda x: (-x.intRectY, x.intRectx))`, i can't really tell what exactly you want since your output is a bit messed up but that could work for you – Primusa Jan 16 '19 at 21:04

how to sort a list in python by two arguments

1 Answers1