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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
CHAR_TO_FLOAT = {
'0' : 0,
'1' : 1,
'2' : 2,
'3' : 3,
'4' : 4,
'5' : 5,
'6' : 6,
'7' : 7,
'8' : 8,
'9' : 9,
'.' : -1
}
def str2float(s):
nums = map(lambda ch: CHAR_TO_FLOAT[ch], s)
point = 0
def to_float(f, n):
nonlocal point
if n == -1:
point = 1
return f
if point == 0:
return f * 10 + n
else:
point = point * 10
return f + n / point
return reduce(to_float, nums, 0.0)
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!')
代码参考:https://github.com/michaelliao/learn-python3/blob/master/samples/functional/do_reduce.py