Question

我是Python的新手，我在列表方面遇到了困难。我希望从列表中的所有值中减去1，除了值10.5。下面的代码给出了x3列表分配索引超出范围的错误。到目前为止的代码：

x2=[10.5, -6.36, 11.56, 19.06, -4.37, 26.56, 9.38, -33.12, -8.44, 0.31, -13.44, - 6.25, -13.44, -0.94, -0.94, 19.06, 0.31, -5.94, -13.75, -23.44, -51.68, 10.5]
x3=[]
i=0
while (i<22):
 if x2[i]==10.5:
    x3[i]=x2[i]
else:
    x3[i]=x2[i]-1
break
#The result I want to achieve is:
#x3=[10.5, -7.36, 10.56, 18.06, -5.37, 25.56, 8.38, -34.12, -9.44, -1.31, -14.44, -7.25, -14.44, -1.94, -1.94, 18.06, -1.31, -6.94, -14.75, -24.44, -52.68, 10.5]

Answer 1

尝试以下方法：

x3 = [((x - 1) if x != 10.5 else x) for x in x2]

Answer 2

x2 = [10.5, -6.36, 11.56, 19.06, -4.37, 26.56, 9.38, -33.12, -8.44, 0.31, -13.44, - 6.25, -13.44, -0.94, -0.94, 19.06, 0.31, -5.94, -13.75, -23.44, -51.68, 10.5]
x3 = map(lambda x: x if x == 10.5 else x - 1, x2)

Python优雅。

Answer 3

x2=[10.5, -6.36, 11.56, 19.06, -4.37, 26.56, 9.38, -33.12, -8.44, 0.31, -13.44, - 6.25, -13.44, -0.94, -0.94, 19.06, 0.31, -5.94, -13.75, -23.44, -51.68, 10.5]
x3=[]
for value in x2:
    if value != 10.5:
        value -= 1
    x3.append(value)

Answer 4

Python的内置函数映射几乎完全适合您手头的情况，使用它并且解决问题的匿名函数变成了单行：

map(lambda x: x if x == 10.5 else x - 1, x2)

或者如果您不习惯使用lambda函数，可以单独定义函数：

def func(x):
    if x == 10.5:
        return x
    else:
        return x - 1

map (func, x2)

Answer 5

地图是最佳选择，但如果你想要不同，请使用reduce：D

>>> x2 = [10.5, -6.36, 11.56, 19.06, -4.37, 26.56, 9.38, -33.12, -8.44, 0.31, -13.44, - 6.25, -13.44, -0.94, -0.94, 19.06, 0.31, -5.94, -13.75, -23.44, -51.68, 10.5]
>>> reduce(lambda x,y: x+[y if y==10.5 else y-1], x2, [])  
[10.5, -7.36, 10.56, 18.06, -5.37, 25.56, 8.38, -34.12, -9.44, -0.69, -14.44, -7.25, -14.44, -1.94, -1.94, 18.06, -0.69, -6.94, -14.75, -24.44, -52.68, 10.5]

Python - 列表中的值的减法

5 个答案: