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将下面的list保留4位小数输出
a = [0.00256,0.00265,0.00254,0.00258]
1，输出之后是浮点数
a = [0.00256,0.00265,0.00254,0.00258]
b = [round(i,4) for i in a]
>>> b
0.0026
0.0027
0.0025
0.0026
值得注意的是round函数有时候结果并不像我们想的那样，比如下面的计算
data是一个数据数组，其中第一行第4列为0.0086809999999999995
上面的结果表明还是使用float(’%.4f’%data[0,3])靠谱。
2，输出之后是字符串
除了使用上面的%.3f%data这种方法外还可以用.format形式
a = [0.00256,0.00265,0.00254,0.00258]
c = ['{:.4f}'.format(i) for i in a]
Out: ['0.0026', '0.0027', '0.0025', '0.0026']