python - 四舍五入数据框列时处理字符串值

Question

我有一个数据框 (df) 看起来像

   DATE_OF_BIRTH           AGE
0     1974-03-28    43.0095412
1      NOT KNOWN     NOT KNOWN
2     1970-11-27    46.3419843
3     1974-05-09    42.8944168
4     1985-03-14    32.0474122

我想将 AGE 列四舍五入到小数点后 3 位，这样所需的输出将如下所示:

   DATE_OF_BIRTH        AGE
0     1974-03-28     43.010
1      NOT KNOWN  NOT KNOWN
2     1970-11-27     46.342
3     1974-05-09     42.894
4     1985-03-14     32.047  

我试过用

df['AGE'] = df['AGE'].round(3) 

但是当遇到字符串(如NOT KNOWN)时，我得到错误:

TypeError: can't multiply sequence by non-int of type 'float' 

如何在舍入数据框列时处理字符串？

Answer 1

我建议使用 to_datetime 将非数字而非日期时间值转换为缺失值和 to_numeric为了避免混合类型 - 带有字符串的数字/日期时间 - 然后数字/类似日期时间的函数失败:

df['DATE_OF_BIRTH'] = pd.to_datetime(df['DATE_OF_BIRTH'], errors='coerce')
df['AGE'] = pd.to_numeric(df['AGE'], errors='coerce').round(3)
print (df)
  DATE_OF_BIRTH     AGE
0    1974-03-28  43.010
1           NaT     NaN
2    1970-11-27  46.342
3    1974-05-09  42.894
4    1985-03-14  32.047