pandas数据预处理实例

我不是女神ヾ 2023-06-19 11:01 118阅读 0赞

1.  排序，默认从小到大排
    
        #By default, pandas will sort the data by the column we specify in ascending order and return a new DataFrame
        # Sorts the DataFrame in-place, rather than returning a new DataFrame.
        #print food_info["Sodium_(mg)"]
        food_info.sort_values("Sodium_(mg)", inplace=True)
        print (food_info["Sodium_(mg)"])
        #Sorts by descending order, rather than ascending.
        food_info.sort_values("Sodium_(mg)", inplace=True, ascending=False)
        print (food_info["Sodium_(mg)"])
    
    运行结果：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70]
2.  打开一个csv文件
    
        import pandas as pd
        import numpy as np
        titanic_survival = pd.read_csv("titanic_train.csv")
        titanic_survival.head()
    
    运行结果：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 1]
3.  计算空值个数
    
        #The Pandas library uses NaN, which stands for "not a number", to indicate a missing value.
        #we can use the pandas.isnull() function which takes a pandas series and returns a series of True and False values
        age = titanic_survival["Age"]
        # print(age.loc[0:10])
        age_is_null = pd.isnull(age)
        # print (age_is_null)
        age_null_true = age[age_is_null]
        # print (age_null_true)
        age_null_count = len(age_null_true)
        print(age_null_count)
    
    运行结果：  
    ![在这里插入图片描述][20191206185708162.png]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20191205222809891.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20191206165252776.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg==,size_16,color_FFFFFF,t_70
[20191206185708162.png]: https://img-blog.csdnimg.cn/20191206185708162.png