[Python-ideas] Make map() better

[Jason H]

> Sent: Wednesday, September 13, 2017 at 11:23 AM
> From: "Edward Minnix" <egregius313 at gmail.com>
> To: "Jason H" <jhihn at gmx.com>
> Cc: Python-Ideas <python-ideas at python.org>
> Subject: Re: [Python-ideas] Make map() better
>
> While I agree that the method calling syntax is nicer, I disagree with flipping the argument error for three main reasons.
> 
> First: it violates the signature entirely
> The signature to map is map(function, *iterables). Python’s map is more like Haskell’s zipWith. Making the function last would either ruin the signature or would slow down performance.
> 
> Second: currying
> If you ever curry a function in Python using functools.partial, having the most common arguments first is crucial. (You’re more likely to apply the same function to multiple iterables than to apply several functions on the same exact iterable).
> 
> Thirdly: the change would make several functional programming packages have incompatible APIs.
> Currently libraries like PyToolz/Cytoolz and funcy have APIs that require function-first argument order. Changing the argument order would be disruptive to most Python FP packages/frameworks.
> 
> So while I agree with you that “iterable.map(fn)” is more readable, I think changing the argument order would be too much of a breaking change, and there is no practical way to add “iterable.map(fn)” to every iterable type.


Thanks for the insights.
I don't think it would be that breaking:

def remap_map(a1, a2):
  if hasattr(a1, '__call__'):
    return map(a1, a2)
  elif hasattr(a2, '__call__'):
    return map(a2,a1)
  else:
    raise NotCallable # Exception neither is callable
    

I'm rather surprised that there isn't a Iterable class which dict and list derive from.
If that were added to just dict and list, I think it would cover 98% of cases, and adding Iterable would be reasonable in the remaining scenarios.