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露心

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1

#编写map/reduce 函数测试
def normalize(name):
    return name[:1].upper()+name[1:].lower()

# 测试:
L1 = ['adam', 'LISA', 'barT']
L2 = list(map(normalize, L1))
print(L2)

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:
from functools import reduce
def prod(L):
    def add(x, y):   
        return x * y
    
    return reduce(add , L)

print('3 * 5 * 7 * 9 =', prod([3, 5, 7, 9]))
if prod([3, 5, 7, 9]) == 945:
    print('测试成功!')
else:
    print('测试失败!')

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

from functools import reduce
DIGITS = {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9}

def str2float(s):
    def ch(ch):
        return DIGITS[ch]
    index = s.find('.')
    #return reduce(lambda x, y:x * 10 + y, map(ch,s[:index]))+0.1*reduce(lambda x, y: x / 10 + y, map(ch, s[index+1:][::-1]))
    return reduce(lambda x, y:x * 10 + y, map(ch,s[:index]))+0.1*reduce(lambda x, y: x / 10 + y, map(ch, s[len(s) - 1 : index:-1]))

print('str2float(\'123.456\') =', str2float('123.456'))
if abs(str2float('123.456') - 123.456) < 0.00001:
    print('测试成功!')
else:
    print('测试失败!')

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