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    <p>Using list comprehensions:</p> <pre><code>&gt;&gt;&gt; [[tuple(map(int, pair)) + (2,) for pair in pairs] for pairs in l] [[(100, 200, 2), (300, 400, 2), (500, 600, 2)], [(100, 200, 2)], [(100, 200, 2)]] </code></pre> <p>Or without the map:</p> <pre><code>&gt;&gt;&gt; [[(int(a), int(b), 2) for a, b in pairs] for pairs in l] [[(100, 200, 2), (300, 400, 2), (500, 600, 2)], [(100, 200, 2)], [(100, 200, 2)]] </code></pre> <h3>Edit</h3> <p>Even with further checks, you can still use list comprehension. I assume that the if/else section you have added to your question should be applied to every pair, and the resulting tuple would be <code>(addr_from, addr_to, 2)</code> then, right?</p> <pre><code>def processPair(a, b): if a.isdigit(): a = int(a) elif a.isalnum(): a = re.sub(r'((?:[A-Z].*?)?(?:\d.*?)?[A-Z]+)(\d+)', r'\1%\2', a) if b.isdigit(): b = int(b) + 2 elif b.isalnum(): b = re.sub(r'((?:[A-Z].*?)?(?:\d.*?)?[A-Z]+)(\d+)', r'\1%\2', b) return (a, b, 2) </code></pre> <p>Here I have defined a function that processes the tuple <code>(a, b)</code> as you did in your question. Note that I have changed it to just modify the values of the variables and return a finished tuple (with the added 2) instead of appending it to some global list.</p> <p>I have also simplified it a bit. <code>a.isdigit() is True</code> is the same as <code>a.isdigit()</code> as that already returns a boolean value. Same for <code>a.isdigit() == False</code>, which is the same as <code>not a.isdigit()</code>. In that situation you can also remove redundant checks. After checking <code>a.isdigit()</code> on the <code>if</code>, you do not need to check its opposite on the <code>elif</code>; it is guaranteed to be false, as you have already checked it before.</p> <p>That being said, when you have said function, you can then use list comprehensions again, to get your output. Of course with your example <code>l</code>, this is a bit boring:</p> <pre><code>&gt;&gt;&gt; [[processPair(*pair) for pair in pairs] for pairs in l] [[(100, 202, 2), (300, 402, 2), (500, 602, 2)], [(100, 202, 2)], [(100, 202, 2)]] </code></pre>
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    1. POIterate over Python list, preserving structure of embedded lists
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    1. COWorked like a charm. Thanks Poke!
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    2. COPoke, it just occurred to me that my question was overly simplified. Because an if, else statement is needed, could you demonstrate how this would be represented without using list comprehensions?
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    3. COA little neater: `[[(int(x), int(y), 2) for x, y in pairs] for pairs in l]`.
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      1. USKarl Knechtel
 

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