解包与压缩 | *sequence, reduce | reduce快速字典重新整理，参考#3

'''
解包与压缩
*sequence,reduce
reduce快速字典重新整理，参考#3
'''
from functools import reduce
primes = [1,2,3,4]
def product(*numbers):
    p = reduce(lambda x, y: x*10+y, numbers)
    print(numbers)
    print(p)
p=product(*primes)  ##*解压，reduce()压缩
p=product(primes,[1])

'''
reduce官方文档定义（部分）：'一次处理两个参数'
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.
————————————————

在迭代sequence(tuple ，list ，dictionary， string等可迭代物)的过程中，
reduce工作过程：
1、首先把 前两个元素传给 函数参数，函数加工后，
2、然后把得到的结果和第三个元素作为两个参数传给函数参数，
3、函数加工后得到的结果又和第四个元素作为两个参数传给函数参数，依次类推
'''
#1
numbers = [1,2,3,4]
p = reduce(lambda x, y: x*10+y, numbers,1)
print(p)#没1输出1234，有1输出11234

#2
from functools import reduce
scientists =({'name':'Alan Turing', 'age':105, 'gender':'male'},
             {'name':'Dennis Ritchie', 'age':76, 'gender':'male'},
             {'name':'Ada Lovelace', 'age':202, 'gender':'female'},
             {'name':'Frances E. Allen', 'age':84, 'gender':'female'})
def reducer(accumulator , value):
    #print(accumulator , value)
    sum = accumulator + value['age']
    return sum
total_age = reduce(reducer, scientists, 0)#0作为reducer初始值，当wequence为空；或作为第一个值
print(total_age)#输出467
#可用一行下面行数实现
sum([x['age'] for x in scientists ])#467

#3  reduce快速字典重新整理，
from functools import reduce
scientists =({'name':'Alan Turing', 'age':105, 'gender':'male'},
             {'name':'Dennis Ritchie', 'age':76, 'gender':'male'},
             {'name':'Ada Lovelace', 'age':202, 'gender':'female'},
             {'name':'Frances E. Allen', 'age':84, 'gender':'female'})
def group_by_gender(accumulator , value):
    accumulator[value['gender']].append(value['name'])
    return accumulator
grouped = reduce(group_by_gender, scientists, {'male':[], 'female':[]})
print(grouped)