1 | initial version |

You don't need Sage for that, you can use pure Python. Here is a solution with list comprehensions:

```
L = [[1,2,3,4],[1,2],[1,4,5,6],[9,10,12,8],[7,3],[4,5,6]]
lengths = list(len(l) for l in L)
maxLength = max( len(l) for l in L )
print(maxLength)
listWithMaxLength = list(l for l in L if len(l) == maxLength)
print(listWithMaxLength)
```

First we create the list `lengths`

with the lengths of the individual lists. Then we can simply get the maximum length as the maximum of that list. Now we create a new list `listWithMaxLength`

where we put all the lists from `L`

in which have this maximum length. I'm sure there are faster methods to do that but for reasonable inputs this should work absolutely fine.

2 | No.2 Revision |

You don't need Sage for that, you can use pure Python. Here is a solution with list comprehensions:

```
L = [[1,2,3,4],[1,2],[1,4,5,6],[9,10,12,8],[7,3],[4,5,6]]
lengths = list(len(l) for l in L)
maxLength = max( len(l) for l in L )
print(maxLength)
listWithMaxLength = list(l for l in L if len(l) == maxLength)
print(listWithMaxLength)
```

First we create the list `lengths`

with the lengths of the individual lists. Then we can simply get the maximum length as the maximum of that list. Now we create a new list `listWithMaxLength`

where we put all the lists from `L`

in which have this maximum ~~length. ~~length (for this you can also use the method `filter`

from python). I'm sure there are faster methods to do that but for reasonable inputs this should work absolutely fine.

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