reduce的用法實(shí)例：
#!/usr/bin/env python3
... #-*-coding:utf-8-*-
...
>>> from functools import reduce
>>>
>>> CHAR_TO_INT = {
...? ? '0':0,
...? ? '1':1,
...? ? '2':2,
...? ? '3':3,
...? ? '4':4,
...? ? '5':5,
...? ? '6':6,
...? ? '7':7,
...? ? '8':8,
...? ? '9':9,
... }
>>>
>>> def str2int(s):
...? ? ints = map(lambda ch: CHAR_TO_INT[ch],s)
...? ? return reduce(lambda x,y:x *10 + y,ints)
...
>>> print(str2int('0'))
0
>>> print(str2int('12300'))
12300
>>> print(str2int('0012345'))
12345
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('0'))
0.0
>>> print(str2float('123.456'))
123.456
>>> print(str2float('123.45600'))
123.456
>>> print(str2float('0.1234'))
0.12340000000000001
>>> print(str2float('.1234'))
0.12340000000000001
>>> print(str2float('120.0034'))
120.0034
