小编Pal*_*ule的帖子

考虑:

#include <vector>
#include <string>
#include <iostream>
using namespace std;

int main()
{
    vector<char> vChar;
    vChar.push_back('a');
    vChar.push_back('b');
    vChar.push_back('c');
    vChar.push_back('d');

    vector<int> vInt;
    vInt.push_back(1);
    vInt.push_back(2);
    vInt.push_back(3);
    vInt.push_back(4);

    cout << "For char vector Size:" << vChar.size() << " Capacity:" << vChar.capacity() << "\n";
    for(int i=0; i < vChar.size(); i++)
    {
        cout << "Data: " << vChar[i] << " Address:" <<  &vChar[i]  << "\n";
    }

    cout << "\nFor int vector Size:" << vInt.size() << " Capacity:" << vInt.capacity() << "\n";
    for (int i = …

import pandas as pd

df = pd.DataFrame([[1,2,3],[4,5,6],[7,8,9],[10,11,12]],columns=['A','B','C'])
df[df['B']%2 ==0]['C'] = 5

我期望这段代码将 C 列的值更改为 5，只要 B 为偶数。但它不起作用。

它返回的表如下

    A   B   C
0   1   2   3
1   4   5   6
2   7   8   9
3   10  11  12

我期待它回来

    A   B   C
0   1   2   5
1   4   5   6
2   7   8   5
3   10  11  12