python|高级函数|filter|map|reduce|sorted

# utils/core.py convert_legacy_filters_into_adhoc()
for filt in filter(lambda x: x is not None, fd[filters]):
    fd[‘adhoc_filters‘].append(to_adhoc(filt, ‘SIMPLE‘, clause))

# 等效写法
reduce(f, [x1, x2, x3, x4]) = f(f(f(x1, x2), x3), x4)

# exampl_1
from functionls import reduce
def add(x, y):
　　return x + y

reduce(add, [1,3,5,7,9])

# exampl_2：把序列[1, 3, 5, 7, 9]变换成整数13579
def fn(x,y):
　　return x*10 + y
reduce(fn, [1,3,5,7,9])

# exampl_2：字符串str也是一个序列,将str转化为int

DIGITS = {‘0‘: 0, ‘1‘: 1, ‘2‘: 2, ‘3‘: 3, ‘4‘: 4, ‘5‘: 5, ‘6‘: 6, ‘7‘: 7, ‘8‘: 8, ‘9‘: 9}

def str2int(s):
    def fn(x, y):
        return x * 10 + y
    def char2num(s):
        return DIGITS[s]
    return reduce(fn, map(char2num, s))

def char2num(s):
    return DIGITS[s]
#使用lambda简化内容
def str2int(s):
    return reduce(lambda x, y: x * 10 + y, map(char2num, s))

# 默认升序排列
sorted([36, 5, -12, 9, -21])
# 按照绝对值排序
sorted([36, 5, -12, 9, -21])　　

# 默认按照ASCII的大小排序，‘Z’ < ‘a‘, 所以‘Z’排在前面
sorted([‘bob‘, ‘about‘, ‘Zoo‘, ‘Credit‘])
# 实现忽略大小写的排序方法： 先将字符串全部转化为大写or小写
sorted([‘bob‘, ‘about‘, ‘Zoo‘, ‘Credit‘], key=str.lower)
# 实现反向排序
sorted([‘bob‘, ‘about‘, ‘Zoo‘, ‘Credit‘], key=str.lower, reverse=True)

# 实现L的按照名称排序

L = [(‘Bob‘, 75), (‘Adam‘, 92), (‘Bart‘, 66), (‘Lisa‘, 88)]

sorted(L, key=lambda x: x[0])