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# 练习函数式编程的map和reduce

from functools import reduce

l = [x for x in range(-10, 10, 2)]

print(l)

l = list(map(abs, l))

print(l)

# reduce是将列表做累计运算

# lambda是匿名函数

num = reduce(lambda x, y: x + y, l)

print(num)

# 将一个字符串转换成整型

def str2int(s):

def char2int(ch):

c = {str(x): x for x in range(10)}

return c[ch]

def fun(n1, n2):

return n1*10 + n2

return reduce(fun, map(char2int, s))

num = str2int('12345')

print(type(num), num)

# 这是使用匿名函数的简便版

def str2int2(s):

ch = {str(x): x for x in range(10)}

return reduce(lambda x, y: x*10+y, map(lambda x: ch[x], s))

num = str2int2('12345')

print(type(num), num)

# 作业：利用map()函数，把用户输入的不规范的英文名字，变为首字母大写，其他小写的规范名字

def normalize(name):

# capitalize()函数是将字符串的首字母大写

return list(map(lambda x: x.capitalize(), name))

L = ['adam', 'LISA', 'barT']

print(normalize(L))

# 作业2：Python提供的sum()函数可以接受一个list并求和，请编写一个prod()函数，可以接受一个list并利用reduce()求积

def prod(x, y):

return x*y

num = reduce(prod, [3, 5, 7, 9])

print(num)

# 作业3：利用map和reduce编写一个str2float函数，把字符串'123.456'转换成浮点数123.456

def str2float(s):

ch = {str(x): x for x in range(10)}

# 先将字符串分割

L = s.split('.')

# 整数部分

n1 = reduce(lambda x, y: x*10 + y, map(lambda x: ch[x], L[0]))

# 小数部分

n2 = reduce(lambda x, y: x * 10 + y, map(lambda x: ch[x], L[1]))

n2 *= 0.1**len(L[1])

return n1+n2

num = str2float('123.456')

print(num)