sorting list of lists

[pframe]

I have the following:

1	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:

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[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]

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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:

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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.

1	# [[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.