dataframe中 常用的 方法

版权声明：本文为博主原创文章，转载请标明出处。 https://blog.csdn.net/chuan403082010/article/details/85163011

新建dataframe

import pandas as pd
a = pd.DataFrame([[1,2,3],
                  [4,5,6],
                  [7,8,9]],columns = ["feature_1", "feature_2", "label"])

读取
import pandas as pd
df = pd.read_csv("datas/hour.csv", sep=",")

删除dataframe列

del df["instant"]

df.drop(columns=["instant","dteday"])

修改dataframe列名

暴力
a.columns = ['a','b','c']

较好的方法
a.rename(columns={'A':'a', 'B':'b', 'C':'c'}, inplace = True)

查看dataframe字段信息

a.info()

修改dataframe列类型

df["instant"] = df["instant"].astype("object")
X[['Global_active_power',"b"]] = X[['Global_active_power',"b"]].astype('float64')

查看dataframe统计信息

a.describe()

获取dataframe部分列

a.iloc[:,0:3]
df.iloc[:,[-1]]
a[["feature_1", "feature_2"]]

获取dataframe列名

df.columns返回一个可迭代对象
for i in df.columns:
    print(i)

获取dataframe的Series

一行
a.iloc[0,:]

一列
a.iloc[:,1]
a["feature_1"]

合并dataframe

横向
pd.concat([a,a],axis=1)

纵向
pd.concat([a,a],axis=0)

替换DF中的字符串

#df.int_rate.replace('%','',inplace = True, regex = True)
a.replace('%','',inplace = True, regex = True)

Dataframe copy

import pandas as pd
a = pd.DataFrame([[1,2,3],
                  [4,5,6],
                  [7,8,9]],columns = ["feature_1", "feature_2", "label"])
b = a.copy()
b.drop(columns=["feature_1"],inplace=True)
a