题目来源:廖雪峰个人网站Python3教程(https://www.liaoxuefeng.com/)
代码思路参考:https://github.com/michaelliao/learn-python3/blob/master/samples/functional/do_reduce.py
Python2实现代码如下:
#encoding=utf-8
flag=0
def str2float(s):
global flag
flag=0 #每次调用函数,就将flag恢复到初始值
CH_TO_NUM={'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9,'.':-1}
nums=map(lambda ch:CH_TO_NUM[ch],s)
def f1(x,y):
global flag
if y==-1:
flag=1
return x #小数点前的整数部分
if flag==0:
return x*10+y
else:
flag=flag*0.1
return x+y*flag
def f2(x,y):
return x*0.1+y
if nums[0]==-1:#特殊情况(.12345),单独处理
return 0.1*reduce(f2,nums[1:][::-1]) #取小数部分并倒序
else :
return reduce(f1,nums)
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!')
print(str2float('0'))
print(str2float('123.456'))
print(str2float('123.45600'))
print(str2float('0.1234'))
print(str2float('.1234'))
print(str2float('120.0034'))