Python Pandas –数据丢失

向右看齐 2023-03-05 11:54 1阅读 0赞

While using pandas, if there is a missing data point, pandas will automatically fill in that missing point with NULL or NAN.

使用熊猫时，如果缺少数据点，熊猫将自动使用NULL或NAN填充该缺失点。

Let's first define a dataFrame using Numpy and Pandas.

让我们首先使用Numpy和Pandas定义一个dataFrame。

import numpy as np
    import pandas as pd
    
    d = {
        'A':[1,2,np.nan],'B':[3,np.nan,np.nan],'C':[4,5,6]}
    df = pd.DataFrame(d)
    print(df)

**Output**

**输出量**

A    B  C
    0  1.0  3.0  4
    1  2.0  NaN  5
    2  NaN  NaN  6

Pandas provide following options to work with the missing data,

熊猫提供以下选项来处理丢失的数据，

### 降低NAN值 **(**Drop NAN values**)** ###

# drops rows with null or NAN values
    print(df.dropna())
    
    '''
         A    B  C
    0  1.0  3.0  4
    '''

# drops columns with null or NAN values
    print(df.dropna(axis=1))
    
    '''
       C
    0  4
    1  5
    2  6
    '''

**Specify a threshold to not drop any number of non-NA values.**

**指定一个阈值，以不丢弃任何数量的非NA值。**

# Does not remove the 2nd row because, 
    # it has less than 2 NAN values.
    print(df.dropna(thresh=2))
    
    '''
         A    B  C
    0  1.0  3.0  4
    1  2.0  NaN  5
    '''

### 填写缺失值 **(**Fill missing values**)** ###

print(df.fillna('empty'))
    
    '''
           A      B  C
    0      1      3  4
    1      2  empty  5
    2  empty  empty  6
    '''

> 翻译自: [https://www.includehelp.com/python/python-pandas-missing-data.aspx][https_www.includehelp.com_python_python-pandas-missing-data.aspx]

[https_www.includehelp.com_python_python-pandas-missing-data.aspx]: https://www.includehelp.com/python/python-pandas-missing-data.aspx