sorting list of lists

[pframe]

I have the following:

list_1=[[499, 943, 1447, 943], [356, 944, 1447, 944], [356, 1226, 1447, 1226], [357, 1228, 1446, 1228], [292, 1456, 1441, 1456], [293, 1457, 1440, 1457], [292, 1991, 1441, 1991], [292, 2096, 1440, 2096], [293, 2098, 1440, 2098]] 

The list is set out in [[x1,y1,x2,y2],......] format and it is based in ascending order based off y1 (it is mean't to go down the page). Every coordinate is mean't to represent a line when joined.

list_1 has 5 lines in total, where as the above list tells me there are 9. Not only that, 3 lines are individual lines and far apart where as 2 lines are near each other together.

So for example:

[499, 943, 1447, 943] & [356, 944, 1447, 944] = 1 line (approx coordinate could be = [356, 944, 1447, 944] ) [356, 1226, 1447, 1226]& [357, 1228, 1446, 1228]=1 line (approx coordinate could be =[356, 1226, 1447, 1226]) [292, 1456, 1441, 1456]& [293, 1457, 1440, 1457] =1 line (approx coordinate could be = [292, 1456, 1441, 1456]) [292, 1991, 1441, 1991] & **[292, 2096, 1440, 2096], [293, 2098, 1440, 2098]** = 2 lines (where the bold coordinates represent the same line) (approx coordinate could be = [292, 1991, 1441, 1991] and [292, 2096, 1440, 2096])

How do I write a function that automatically filters those coordinates and returns the right amount of lines i.e 5 and gives an approximation of where that line is.

[Larz60+]

what have you tried?
show code working or not

[pframe]

from operator import itemgetter import itertools list_1=[[499, 943, 1447, 943], [356, 944, 1447, 944], [356, 1226, 1447, 1226], [357, 1228, 1446, 1228], [292, 1456, 1441, 1456], [293, 1457, 1440, 1457], [292, 1991, 1441, 1991], [292, 2096, 1440, 2096], [293, 2098, 1440, 2098]] x1_value=list(map(itemgetter(0), a)) #sort out the x1 values lowest_x=min(x1_value) #finds the lowest x1 value #now i will replace all x1 value with the lowest so it is consistent x1 i=0 for i in range(0,len(a)): a[i][0]=lowest_x i+=1 # [[292, 943, 1447, 943], [292, 944, 1447, 944], #[292, 1226, 1447, 1226], [292, 1228, 1446, 1228], #[292, 1456, 1441, 1456], [292, 1457, 1440, 1457], #[292, 1991, 1441, 1991], [292, 2096, 1440, 2096], #[292, 2098, 1440, 2098]] y1=list( map(itemgetter(1), a )) #puts y1 in a list # narrow downs your y1 value index = 1 while index < len(y1): #print(f"comparing {y1[index-1]} with {y1[index]} y1 list {y1}") if abs(y1[index] - y1[index - 1]) < 4: del y1[index] else: index += 1 #print(a) #print(y1) #now i will check if my y1 list is in a. Where rr represent a and pp represent y rr = a pp = [[y] ] result = [] ignore = [] for item in itertools.chain.from_iterable(pp): for pair in rr: if item in pair: #print('Yepp, {} is in {}. Ignoring!'.format(item, pair)) ignore.append(pair) elif not pair in result and pair not in ignore: result.append(pair) print(a) print('Result: {}'.format(ignore)) # [[292, 943, 1447, 943], [292, 1226, 1447, 1226], [292, 1456, 1441, 1456], [292, 1991, 1441, 1991], [292, 2096, 1440, 2096]]

As you can see it does the job, but is there a simple solution or a cleaner code that runs faster?

[Larz60+]

how about:

list_1 = [ [499, 943, 1447, 943], [356, 944, 1447, 944], [356, 1226, 1447, 1226], [357, 1228, 1446, 1228], [292, 1456, 1441, 1456], [293, 1457, 1440, 1457], [292, 1991, 1441, 1991], [292, 2096, 1440, 2096], [293, 2098, 1440, 2098], ] list_2 = sorted(list_1, key=lambda sublist: sublist[0]) print(f"list_2 = [") for alist in list_2: print(f" {alist}") print(f"]")

Gives:

Output:
list_2 = [ [292, 1456, 1441, 1456] [292, 1991, 1441, 1991] [292, 2096, 1440, 2096] [293, 1457, 1440, 1457] [293, 2098, 1440, 2098] [356, 944, 1447, 944] [356, 1226, 1447, 1226] [357, 1228, 1446, 1228] [499, 943, 1447, 943] ]

[pframe]

The result is something like this.

 # [[292, 943, 1447, 943], [292, 1226, 1447, 1226], [292, 1456, 1441, 1456], [292, 1991, 1441, 1991], [292, 2096, 1440, 2096]] 

list_1 represents a set of points [x1,y1,x2,y2] which form a line. So if you draw it out you can see what I am talking about. My solution above, basically eliminates those pseudo points/lines and returns one from each subset.

How I know it is there are 5 lines and in your solution it has more than 5 lines.

[Larz60+]

There are 9 sub lists in your list_1 data.