pandas删除行列或增加行列

数据展示

dic = {'id':[1,2,3,4,5,6,2],'dishes_name':['蒙古烤羊腿','大蒜苋菜',
        '蒜香包','干锅田鸡','大蒜苋菜','芝麻烤紫菜','大蒜苋菜'],
       'amount':[48,20,32,56,20,32,20]}
data = pd.DataFrame(dic,columns=['id','dishes_name','amount'])
data

①删除行

• 删除某列指定的数据

#删除某列指定的数据
ind=data['dishes_name']=='大蒜苋菜'
data.drop(data[ind].index)

• 删除['dishes_name','amount']两列重复值的行

#删除['dishes_name','amount']两列重复值的行
ind1 = data.drop_duplicates(subset=['dishes_name','amount'])
ind1

• 不指定subset时，默认删除重复的样本数据

#不指定subset时，默认删除重复的样本数据
data.drop_duplicates()

②删除空值行 : data.dropna(axis=0, how='any', thresh=None, subset=None, inplace=False)

axis=0:删除的是行，默认为0；

how：对数据列的判断，'any'是指有空值就删除，‘all’是当所有列在该行为空值是就删除

subset:指定判断的列

inplace：指处理数据后是否原数据也改变

dic = {'id':[1,2,3,4],'dishes_name':['蒙古烤羊腿','大蒜苋菜',
        '蒜香包','大蒜苋菜'],
       'amount':[48,20,32,pd.NaT]}
data = pd.DataFrame(dic,columns=['id','dishes_name','amount'])
data

•  删除指定['dishes_name','amount']的列有空值的行

data.dropna(axis=0,subset=['dishes_name','amount'],how='any')

•  删除指定['dishes_name','amount']的列都有空值的行

data.dropna(axis=0,subset=['dishes_name','amount'],how='all')

②删除列

• del只能删除一列数据，且改变原数据（不建议使用）

del data['amount']

•  drop可以删除多列，但一定要指定axis=1，否则会报错

data.drop(['amount','dishes_name'],axis=1)

③添加行数据

数据展示

dic = {'id':[1,2,3,4,5,6,2],'dishes_name':['蒙古烤羊腿','大蒜苋菜',
        '蒜香包','干锅田鸡','大蒜苋菜','芝麻烤紫菜','大蒜苋菜'],
       'amount':[48,20,32,56,20,32,20]}
data = pd.DataFrame(dic,columns=['id','dishes_name','amount'])
data

•  添加ann_columns列为空值

import numpy as np

data['ann_columns'] = np.nan
data

•  添加行为空

data.loc[99,:]=np.nan
data