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POSorting List of Tuples with Multiconditions in Python
 

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  1. POSorting List of Tuples with Multiconditions in Python
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    <p>I'm using Python 2.6.2. I have a list of tuples <code>pair</code> which I like to sort using two nested conditions. </p> <ol> <li>The tuples are first sorted in descending count order of <code>fwd_count</code>,</li> <li>If the value of count is the same for more than one tuple in <code>fwd_count</code>, only those tuples having equal count need to be sorted in descending order based on values in <code>rvs_count</code>.</li> <li>The order does not matter and the positioning can be ignored, if a) tuples have the same count in <code>fwd_count</code> and also in <code>rvs_count</code>, or a) tuples have the same count in <code>fwd_count</code> and does not exist in <code>rvs_count</code> </li> </ol> <p>I managed to write the following code:</p> <pre><code>pair=[((0, 12), (0, 36)), ((1, 12), (0, 36)), ((2, 12), (1, 36)), ((3, 12), (1, 36)), ((1, 36), (4, 12)), ((0, 36), (5, 12)), ((1, 36), (6, 12))] fwd_count = {} rvs_count = {} for link in sorted(pair): fwd_count[link[0]] = 0 rvs_count[link[1]] = 0 for link in sorted(pair): fwd_count[link[0]] += 1 rvs_count[link[1]] += 1 #fwd_count {(6, 12): 1, (5, 12): 1, (4, 12): 1, (1, 36): 2, (0, 36): 2} #rvs_count {(3, 12): 1, (1, 12): 1, (1, 36): 2, (0, 12): 1, (2, 12): 1, (0, 36): 1} fwd_count_sort=sorted(fwd_count.items(), key=lambda x: x[1], reverse=True) rvs_count_sort=sorted(rvs_count.items(), key=lambda x: x[1]) #fwd_count_sort [((1, 36), 2), ((0, 36), 2), ((6, 12), 1), ((5, 12), 1), ((4, 12), 1)] #rvs_count_sort [((3, 12), 1), ((1, 12), 1), ((1, 36), 2), ((0, 12), 1), ((2, 12), 1), ((0, 36), 1)] </code></pre> <p>The result I am looking for is:</p> <pre><code>#fwd_count_sort_final [((0, 36), 2), ((1, 36), 2), ((6, 12), 1), ((5, 12), 1), ((4, 12), 1)] </code></pre> <p>Where the position of <code>(1, 36)</code> and <code>(0, 36)</code> have swapped position from the one in <code>fwd_count_sort</code>.</p> <p>Question:</p> <ol> <li>Is there a better way to do multi condition sorting using <code>fwd_count</code> and <code>rvs_count</code> information at the same time? (Only the tuples are important, the sort value need not be recorded.), or</li> <li>Would I need to sort it individually for each conditions (as I did above) and try to find mean to integrate it to get the result I wanted? </li> </ol> <p>I am currently working on item #2 above, but trying to learn if there are any simpler method. </p> <p>This is the closest I can get to what I am looking for "Bidirectional Sorting with Numeric Values" at <a href="http://stygianvision.net/updates/python-sort-list-object-dictionary-multiple-key/" rel="nofollow">http://stygianvision.net/updates/python-sort-list-object-dictionary-multiple-key/</a> but not sure I can use that if I create a new dictionary with {tuple: {fwd_count : rvs_count}} relationship.</p> <p><strong>Update: 12 November 2012 -- SOLVED</strong></p> <p>I have managed to solve this by using list. The below are the codes, hope it is useful for those whom are working to sort multi condition list.</p> <pre><code>#pair=[((0, 12), (0, 36)), ((1, 12), (1, 36)), ((2, 12), (0, 36)), ((3, 12), (1, 36)), ((1, 36), (4, 12)), ((0, 36), (5, 12)), ((1, 36), (6, 12))] rvs_count = {} fwd_count = {} for link in sorted(pair): rvs_count[link[0]] = 0 fwd_count[link[1]] = 0 for link in sorted(pair): rvs_count[link[0]] += 1 fwd_count[link[1]] += 1 keys = [] for link in pair: if link[0] not in keys: keys.append(link[0]) if link[1] not in keys: keys.append(link[1]) aggregated = [] for k in keys: a = -1 d = -1 if k in fwd_count.keys(): a = fwd_count[k] if k in rvs_count.keys(): d = rvs_count[k] aggregated.append(tuple((k, tuple((a,d)) ))) def compare(x,y): a1 = x[1][0] d1 = x[1][1] a2 = y[1][0] d2 = y[1][1] if a1 &gt; a2: return - a1 + a2 elif a1 == a2: if d1 &gt; d2: return d1 - d2 elif d1 == d2: return 0 else: return d1 - d2 else: return - a1 + a2 s = sorted(aggregated, cmp=compare) print(s) j = [v[0] for v in s] print(j) </code></pre> <p>Thanks to Andre Fernandes, Brian and Duke for giving your comments on my work</p>
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    1. USSaravanan K
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    1. COCould you explain why you want ((6, 12), 1) sorted before ((5, 12), 1) in the result?
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      1. POSorting List of Tuples with Multiconditions in Python
      1. USwim
    2. CO@wim I missed to mention those who has same count in "fwd_count" and also in "rvs_count" (if exist) the order does not matter. Since fwd_count is sorted in descending order, whenever the count is same, python list then sort it descending based on "link" id, since ((6, 12), 1) > ((5, 12), 1), the tuple ((6, 12), 1) is sorted before ((5, 12), 1). But it does not matter in my case. Hope I have clarified well. Thanks for asking.
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      1. POSorting List of Tuples with Multiconditions in Python
      1. USSaravanan K
    3. COI do not understand the pattern? Why is everything being switched?
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      1. USenginefree
 

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