Question

我有一个示例熊猫数据框，如下所示：

delme = {
    "c1": [1, 2, 3],
    "c2": ["he", "she", "he"],
    "c3": [1.3, 1.4, 1.5],
    "pre_c1": ["x1", "x2", "x3"],
    "pre_c2": ["y1", "y2", "y3"],
    "pre_c3": ["z1", "z2", "z3"],
    "npre_c1": ["x1", "x2", "x3"],
    "npre_c2": ["y1", "y2", "y3"]
}

delmedf = pd.DataFrame(delme)

c1  c2  c3  pre_c1  pre_c2  pre_c3  npre_c1 npre_c2
1   he  1.3     x1      y1      z1       x1      y1
2   she 1.4     x2      y2      z2       x2      y2
3   he  1.5     x3      y3      z3       x3      y3

我想从pre_数据框中选择所有带有前缀npre_和c3的列以及列delmedf。我该怎么办？

到目前为止，我已尝试分别捕获它们，然后将它们与axis=1合并，如下所示：

df1 = delmedf[delmedf.columns[(pd.Series(delmedf.columns).str.contains("pre_"))]]
df2= delmedf[[c2]]
data_X = pd.concat([df1, df2], axis=1)

但是，只要我想引入另一个str.contains("npre_")条件，上述方法就会失败： df1 = delmedf[delmedf.columns[(pd.Series(delmedf.columns).str.contains("pre_")) or (pd.Series(delmedf.columns).str.contains("npre_"))]]

上面的语句出现的错误是：

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

谢谢。

Answer 1

使用：

m=delmedf.columns.str.contains('pre_')|(delmedf.columns=='c3')
delmedf[delmedf.columns[m]]

输出

    c3 pre_c1 pre_c2 pre_c3 npre_c1 npre_c2
0  1.3     x1     y1     z1      x1      y1
1  1.4     x2     y2     z2      x2      y2
2  1.5     x3     y3     z3      x3      y3

Answer 2

您可以使用这样的正则表达式：

df.loc[:,np.ndarray.flatten(df.columns.str.extract(r'(^[n]?pre_.*|c3)').dropna().to_numpy())]                                                                                        

    c3 pre_c1 pre_c2 pre_c3 npre_c1 npre_c2
0  1.3     x1     y1     z1      x1      y1
1  1.4     x2     y2     z2      x2      y2
2  1.5     x3     y3     z3      x3      y3

Answer 3

还有一个选择：）

MySql.Data.MySqlClient.MySqlException: 'Authentication to host 'ip' for user 'root' using method 'mysql_native_password' failed with message: Access denied for user 'root'@'my-ip' (using password: YES)'

结果：

#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>

int main(void)
{
    string message=get_string("Enter a message to encrypt: \n");
    int key=get_int("Enter a key to encrypt the message: \n");
    char m[strlen(message)];
    strcpy(m, message);
    for(int i=0; i<strlen(message); i++)
    {
        char letter=m[i];
        if(isalpha(m[i])||isupper(m[i])||islower(m[i]))
        {
            if(letter>='a'&&letter<='z')
            {
                letter=letter+key;
                if(letter>'z')
                {
                    letter=letter-'z'+'a'-1;
                    letter=m[i];
                }
                letter=m[i];
            }
            else if(letter>='A'&&letter<='Z')
            {
                letter=letter+key;
                if(letter>'Z')
                {
                    letter=letter-'Z'+'A'-1;
                    letter=m[i];
                }
                letter=m[i];
            }
        }
        printf("%c", m[i]);
    }
    printf("\n");
    return 0;
}

如何在Pandas数据框中选择所有相同的前缀列以及其他列？

3 个答案: