python中的顺序函数映射 [英] Sequential function mapping in python

问题描述

我在列表中有很多功能:

I have a bunch of functions in a list:

funcs = [f1, f2, f3, f4, f5]

和所有函数都返回一个参数，例如.

and all of the functions take in return a single argument, eg.

f1 = lambda x: x*2

我想将所有这些功能映射在一起

I'd like to map all these functions together

result = lambda x: f5(f4(f3(f2(f1(x)))))

或遍历funcs

def dispatch(x):
    for f in funcs:
        x = f(x)
    return x

dispatch可以正常工作，但是我想不出一种使用iterools的干净方法.是否有可能?这个顺序函数映射习惯用法有名字吗?

dispatch works fine, but I couldn't figure out a clean way to do this using iterools. Is it possible? Does this sequential function mapping idiom have a name?

推荐答案

在这里使用itertools没有意义；您正在产生一个输出，并且无法将其应用于无限迭代.您必须在输入中具有 finite 个可迭代的函数，此函数才能完全起作用.

There is no point in using itertools here; you are producing one output, and you could not apply this to an infinite iterable. You have to have a finite number of functions in the input iterable for this to work at all.

使用 reduce()函数:

from functools import reduce

x = reduce(lambda res, func: func(res), funcs, x)

functools.reduce()导入可帮助上述工作Python 2和3.

The functools.reduce() import helps the above work in both Python 2 and 3.

reduce()和map()，filter()以及(c3)是

reduce(), together with map(), filter() and, yes, itertools, is an often used tool in functional programming.

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