>>> 0.4-0.3 结果为啥是 0.10000000000000003 about wtfpython-cn HOT 4 CLOSED

[ins] In [14]: from decimal import *                                                                                                    

[ins] In [15]: getcontext().prec                                                                                                        
Out[15]: 28

[ins] In [16]: Decimal.from_float(0.3)                                                                                                  
Out[16]: Decimal('0.299999999999999988897769753748434595763683319091796875')

[ins] In [17]: Decimal.from_float(0.1 + 0.2)                                                                                            
Out[17]: Decimal('0.3000000000000000444089209850062616169452667236328125')


[ins] In [18]: 0.3                                                                                                                      
Out[18]: 0.3

[ins] In [19]: 0.1 + 0.2                                                                                                                
Out[19]: 0.30000000000000004

[ins] In [23]: Decimal.from_float(0.30000000000000003) # 和0.1+0.2对应的一样，也就是输入和输出不一样                                                                                 
Out[23]: Decimal('0.3000000000000000444089209850062616169452667236328125')