30 lines
1.2 KiB
Markdown
30 lines
1.2 KiB
Markdown
---
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title: merge
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tags: list,math,advanced
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---
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Merges two or more lists into a list of lists, combining elements from each of the input lists based on their positions.
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Use `max` combined with list comprehension to get the length of the longest list in the arguments.
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Use `range()` in combination with the `max_length` variable to loop as many times as there are elements in the longest list.
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If a list is shorter than `max_length`, use `fill_value` for the remaining items (defaults to `None`).
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[`zip()`](https://docs.python.org/3/library/functions.html#zip) and [`itertools.zip_longest()`](https://docs.python.org/3/library/itertools.html#itertools.zip_longest) provide similar functionality to this snippet.
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```py
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def merge(*args, fill_value=None):
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max_length = max([len(lst) for lst in args])
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result = []
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for i in range(max_length):
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result.append([
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args[k][i] if i < len(args[k]) else fill_value for k in range(len(args))
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])
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return result
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```
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```py
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merge(['a', 'b'], [1, 2], [True, False]) # [['a', 1, True], ['b', 2, False]]
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merge(['a'], [1, 2], [True, False]) # [['a', 1, True], [None, 2, False]]
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merge(['a'], [1, 2], [True, False], fill_value = '_') # [['a', 1, True], ['_', 2, False]]
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```
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