【Python3】04、内置数据结构
#############In : mapping = {str(x):x for x in range(9)}
In : mapping
Out: {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8}
In : s.partition('.')
Out: ('123', '.', '456')
In : s = "123"
In : s.partition('.')
Out: ('123', '', '')
In : s = "12.3"
In : s.partition('.')
Out: ('12', '.', '3')
In : s = "123.456"
In : i, _, f = s.partition('.')
In : ret = 0
In : for idx, x in enumerate(i[::-1]):
...: ret += mapping * 10 ** idx
...:
In : ret
Out: 123
In : for idx, x in enumerate(f):
...: ret += mapping / 10 ** (idx+1)
...:
In : ret
Out: 123.456 #结果可能会有精度的问题
###先全部当成整数来运算###
In : ret = 0
In : for idx, x in enumerate((i+f)[::-1]):
...: ret += mapping * 10 ** idx
...:
In : ret / 10 ** len(f)
Out: 123.456 #精度损失会少一点
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