Pandas从每行列表中减去相同的数字

Question

我将pandas数据帧设为：

#include <iostream>
using namespace std;

class Rational {
    private:
        int n; // (fraction numerator)
        int d; // (fraction denominator).

    public:
        Rational() {
            n = 0;
            d = 1;
        }
        Rational(int num, int denom) {
            n = num;
            d = denom;
        }

        friend istream& operator >> (istream& in_str, Rational& right);
        friend ostream& operator << (ostream& out_str, const Rational& right);
        friend Rational operator+ (const Rational&, const Rational&);

        //friend istream& operator >> (istream& in_str, Rational& right);
        //friend ostream& operator <<(ostream& out_str, const Rational& right);
        //friend Rational operator+(const Rational&, const Rational&);


};




int main()
{
    cout << "Testing declarations" << endl;
    cout << "Rational x, y(2), z(-5,-6), w(1,-3);" << endl;
    return 0;
}

istream& operator >> (istream& in_str, Rational& right) {
    cin >> n.right;
}
ostream& operator << (ostream& out_str, const Rational& right); {
    cout << out_str;
}
Rational operator+(const Rational&, const Rational&); {
    cout << Rational;
}

我想执行以下操作：

df1['A'].ix[1:3]
2017-01-01 02:00:00    [33, 34, 39]
2017-01-01 03:00:00    [3, 43, 9]

df2['B'].ix[1:3]
2017-01-01 02:00:00    2
2017-01-01 03:00:00    3

预期结果是：

difference = df1 - df2

即。来自(df1 - df2).ix[1:3] 2017-01-01 02:00:00 [31, 32, 37] 2017-01-01 03:00:00 [0, 40, 6]

中相应列表的df2中的减去数字

df1的每个列表都有相同的大小。

我无法想到比df1更好的方式。

Answer 1

我无法分辨df1中的对象是什么。可能list可能np.array？ IDK？

最好我创建自己的例子

A = pd.Series([[33, 34, 39], [3, 43, 9]])
B = pd.Series([2, 3])

选项1
apply(np.asarray)

A.apply(np.asarray) - B

0    [31, 32, 37]
1      [0, 40, 6]
dtype: object

选项2
更丑但更快，见下文

pd.Series((np.array(A.values.tolist()) - B.values[:, None]).tolist(), A.index)

0    [31, 32, 37]
1      [0, 40, 6]
dtype: object

<强> 定时

Answer 2

您可以将列值从列表转换为numpy数组，然后执行df1.A - df2.B：

df1.A = df1.A.map(np.array)
difference = df1.A - df2.B