Is there a zip-like function that pads to longest length?

Question

Is there a built-in function that works like `zip()` but that will pad the results so that the length of the resultant list is the length of the longest input rather than the shortest input? ``` >>> a = ['a1'] >>> b = ['b1', 'b2', 'b3'] >>> c = ['c1', 'c2'] >>> zip(a, b, c) [('a1', 'b1', 'c1')] >>> What command goes here? [('a1', 'b1', 'c1'), (None, 'b2', 'c2'), (None, 'b3', None)] ```

Accepted Answer

In Python 3 you can use `itertools.zip_longest`

```
>>> list(itertools.zip_longest(a, b, c))
[('a1', 'b1', 'c1'), (None, 'b2', 'c2'), (None, 'b3', None)]
```

You can pad with a different value than `None` by using the `fillvalue` parameter:

```
>>> list(itertools.zip_longest(a, b, c, fillvalue='foo'))
[('a1', 'b1', 'c1'), ('foo', 'b2', 'c2'), ('foo', 'b3', 'foo')]
```

With Python 2 you can either use `itertools.izip_longest` (Python 2.6+), or you can use `map` with `None`. It is a little known feature of `map` (but `map` changed in Python 3.x, so this only works in Python 2.x).

```
>>> map(None, a, b, c)
[('a1', 'b1', 'c1'), (None, 'b2', 'c2'), (None, 'b3', None)]
```

Is there a zip-like function that pads to longest length?

Solution

Problem