pandas.DataFrame删除/选取含有特定数值的行或列

秒速五厘米 2024-02-19 15:29 20阅读 0赞

1.删除/选取某列含有特殊数值的行  
import pandas as pd  
import numpy as np

a=np.array(\[\[1,2,3\],\[4,5,6\],\[7,8,9\]\])  
df1=pd.DataFrame(a,index=\[‘row0’,‘row1’,‘row2’\],columns=list(‘ABC’))  
print(df1)  
df2=df1.copy()

\#删除/选取某列含有特定数值的行  
\#df1=df1\[df1\[‘A’\].isin(\[1\])\]  
\#df1\[df1\[‘A’\].isin(\[1\])\] 选取df1中A列包含数字1的行

df1=df1\[~df1\[‘A’\].isin(\[1\])\]  
\#通过~取反，选取不包含数字1的行  
print(df1)  
运行结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xvbmdlMjAxMTExMDQ_size_16_color_FFFFFF_t_70]

2.删除/选取某行含有特殊数值的列  
\#删除/选取某行含有特定数值的列  
cols=\[x for i,x in enumerate(df2.columns) if df2.iat\[0,i\]==3\]  
\#利用enumerate对row0进行遍历，将含有数字3的列放入cols中  
print(cols)

\#df2=df2\[cols\] 选取含有特定数值的列  
df2=df2.drop(cols,axis=1) \#利用drop方法将含有特定数值的列删除  
print(df2)  
运行结果：  
![在这里插入图片描述][2019010623404164.png]

3.删除含有空值的行或列  
实现思路：利用pandas.DateFrame.fillna对空值赋予特定值，再利用上文介绍的方法找到这些含有特定值的行或列去除即可。

import pandas as pd  
import numpy as np

df1 = pd.DataFrame(  
\[  
\[np.nan, 2, np.nan, 0\],  
\[3, 4, np.nan, 1\],  
\[np.nan, np.nan, np.nan, 5\],  
\[np.nan, 3, np.nan, 4\]  
\],columns=list(‘ABCD’))  
print(df1)  
df2=df1.copy()

df1\[‘A’\]=df1\[‘A’\].fillna(‘null’) \#将df中A列所有空值赋值为’null’  
print(df1)  
df1=df1\[~df1\[‘A’\].isin(\[‘null’\])\]  
print(df1)

\#删除某行空值所在列

df2\[0:1\]=df2\[0:1\].fillna(‘null’)  
print(df2)  
cols=\[x for i,x in enumerate(df2.columns) if df2.iat\[0,i\]==‘null’\]  
print(cols)  
df2=df2.drop(cols,axis=1)  
print(df2)  
运行结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xvbmdlMjAxMTExMDQ_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xvbmdlMjAxMTExMDQ_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/53aa14cd568246ceb2eb708416201f98.png
[2019010623404164.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/3daeb3d2b9e045c0a72ff8e24bde93b3.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xvbmdlMjAxMTExMDQ_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/afb3e90355f449969bba3d01e811667b.png