python-3.x - 为什么减少要求参数的函数

Question

我已经用 reduce 内置函数编写了这些代码行，但它显示给定参数的错误。

错误：

TypeError Traceback (last last call last) in 4 5 lst = [1,2,3] ----> 6 reduce(d_n, lst)

TypeError: d_n() 接受 1 个位置参数，但给出了 2 个

from functools import reduce
def d_n(digit):
    return(digit)

lst = [1,2,3]
reduce(d_n, lst)

标签： python-3.x

Answer 1

reduce(...)
    reduce(function, sequence[, initial]) -> value

    Apply a function of two arguments cumulatively to the items of a sequence,
    from left to right, so as to reduce the sequence to a single value.
    For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates
    ((((1+2)+3)+4)+5).  If initial is present, it is placed before the items
    of the sequence in the calculation, and serves as a default when the
    sequence is empty.

关键点：两个参数的函数

您的d_n()函数只接受一个参数，这使得它与reduce