`six` was instrumental in repairing the Python schism by giving people a way to incrementally move their 2.7 code to Python 3, and write code that was compatible in both. The six project didn't exist at first and the path to Python 3 was too painful without it. Six solved all that by smoothing over built-in libraries with different casing between versions, incompatible core libraries, the addition of unicode strings, print changing to a function, etc, etc. Perl 5 to Perl 6 (aka Raku) never got that.
3. six
`six` was instrumental in repairing the Python schism by giving people a way to incrementally move their 2.7 code to Python 3, and write code that was compatible in both. The six project didn't exist at first and the path to Python 3 was too painful without it. Six solved all that by smoothing over built-in libraries with different casing between versions, incompatible core libraries, the addition of unicode strings, print changing to a function, etc, etc. Perl 5 to Perl 6 (aka Raku) never got that.