4 ms·

You don't. Use generator syntax, which is really the more pythonic way to it. >>> iter = [1,2,3,4] >>> f1 = lambda x: x*2 >>> f2 = lambda x: x+4

• BeetleB 2y ago
  First off, writing f3(f2(f1(x))) is painful - keeping track of parentheses. If you want to insert a function in the middle of the chain you have some bookkeeping to do. Second, that's all good and well if all you want to do is map. But what if you need combinations of map and filter as well? You're suddenly dealing with nested comprehensions, which few people like. In F#, it'll still be: iter |> f1 |> f2 |> f3 |> f4 Here's an example from real code I wrote: graph |> Map.filter isSubSetFunc |> Map.filter doesNotContainFunc |> Map.values |> Set.ofSeq This would not be fun to write in List Comprehensions, but you could manage (only two list comprehensions). Now here's other code: graph |> removeTerminalExerciseNodes |> Map.filter isEmpty |> Map.keys |> Seq.map LookUpFunc |> Seq.map RemoveTrivialNodes |> Seq.sortBy GetLength |> Seq.rev |> Seq.toList BTW, some of the named functions above are defined with their own chain of maps and filters.
  • Izkata 2y ago
    An alternative for python is to flip what you're iterating over at the outermost level. It's certainly not as clean as F# but neither is it as bad as the original example if there's a lot of functions: iter = [1,2,3,4] f1 = lambda x: x*2 f2 = lambda x: x+4 f3 = lambda x: x*1.25 result = iter for f in [f1, f2, f3]: result = [f(v) for v in result] Then the list comprehension can be moved up to mimic more closely what you're doing with F#, allowing for operations other than "map": result = iter for f in [ lambda a: [f1(v) for v in a], lambda a: [f2(v) for v in a], lambda a: [f3(v) for v in a], ]: result = f(result) And a step further if you don't like the "result" reassignment: from functools import reduce result = reduce(lambda step, f: f(step), [ lambda a: [f1(v) for v in a], lambda a: [f2(v) for v in a], lambda a: [f3(v) for v in a], ], iter)
    • BeetleB 2y ago
      Fair, but how would it look if you had some filters and reduces thrown in the middle? In my F# file of 300 lines[1], I do this chaining over 20 times in various functions. Would you really want to write the Python code your way every time, or wouldn't you prefer a simpler syntax? People generally don't do it your way often because it has a higher mental burden than it does with the simple syntax in F# and other languages. I don't do it 20 times because of an obsession, but because it's natural. [1] Line count is seriously inflated due to my habit of chaining across multiple lines as in my example above.
      • Izkata 2y ago
        My example was just a way to do it with plain python and nothing special. There are libraries that use operator overloading to get more F#-style syntax. For example: https://ryi.medium.com/flexible-piping-in-python-with-pipey-e8762db3a4ab https://ryi.medium.com/flexible-piping-in-python-with-pipey-... And another mentioned there: https://pypi.org/project/pipe/ https://pypi.org/project/pipe/
        • kingdomcome50 2y ago
          I think we can just let this rest. These kinds of operations are not as ergonomic in python. That's pretty clear. No example provided is even remotely close to the simplicity of the F# example. Acquiesce.
          • Izkata 2y ago
            You do realize this was in my original comment, right? > It's certainly not as clean as F# but neither is it as bad as the original example if there's a lot of functions
            • z500 2y ago
              The fact is the language just works against you in this area if you have to jump through hoops to approximate a feature other languages just have. And I don't even mean extra syntax like F#'s pipe operators (although I do love them). Just swapping the arguments so you could chain the calls would look a lot better, if a little LISPy. It really is that bad.
• Izkata 2y ago
  You're not using generator syntax anywhere in that example.
• itishappy 2y ago
  Generators require a __next__ method, yield statement, or generator comprehension. What you've got is lambdas and a list comprehension. Rewriting using generators would look something like: items = [1,2,3,4] gen1 = (x*2 for x in items) gen2 = (x+4 for x in gen1) gen3 = (x*1.25 for x in gen2) result = list(gen3) It's nicer in a way, certainly closer to the pipe syntax the commenter your replying to is looking for, but kind of janky to have to name all the intermediate steps.
• cma 2y ago
  f3(f2(f1 This is still backwards?