向Pandas中的现有DataFrame添加新列

让我们讨论一下如何向Pandas中的现有DataFrame添加新列。我们可以通过多种方式完成此任务。
方法1：通过将新列表声明为一列。

# Import pandas package import pandas as pd# Define a dictionary containing Students data data = https://www.lsbin.com/{'Name' : [ 'Jai' , 'Princi' , 'Gaurav' , 'Anuj' ], 'Height' : [ 5.1 , 6.2 , 5.1 , 5.2 ], 'Qualification' : [ 'Msc' , 'MA' , 'Msc' , 'Msc' ]}# Convert the dictionary into DataFrame df = pd.DataFrame(data)# Declare a list that is to be converted into a column address = [ 'Delhi' , 'Bangalore' , 'Chennai' , 'Patna' ]# Using 'Address' as the column name # and equating it to the list df[ 'Address' ] = address# Observe the result df

输出如下：

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请注意, 列表的长度应与索引列的长度匹配, 否则将显示错误。
方法2：通过使用DataFrame.insert() 它使你可以自由地在我们喜欢的任何位置(而不仅仅是在结尾处)添加一列。它还提供了用于插入列值的不同选项。

# Import pandas package import pandas as pd# Define a dictionary containing Students data data = https://www.lsbin.com/{'Name' : [ 'Jai' , 'Princi' , 'Gaurav' , 'Anuj' ], 'Height' : [ 5.1 , 6.2 , 5.1 , 5.2 ], 'Qualification' : [ 'Msc' , 'MA' , 'Msc' , 'Msc' ]}# Convert the dictionary into DataFrame df = pd.DataFrame(data)# Using DataFrame.insert() to add a column df.insert( 2 , "Age" , [ 21 , 23 , 24 , 21 ], True )# Observe the result df

输出如下：

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【向Pandas中的现有DataFrame添加新列】方法3：使用Dataframe.assign()方法
此方法将创建一个新数据框, 并将新列添加到旧数据框。

# Import pandas package import pandas as pd# Define a dictionary containing Students data data = https://www.lsbin.com/{'Name' : [ 'Jai' , 'Princi' , 'Gaurav' , 'Anuj' ], 'Height' : [ 5.1 , 6.2 , 5.1 , 5.2 ], 'Qualification' : [ 'Msc' , 'MA' , 'Msc' , 'Msc' ]}# Convert the dictionary into DataFrame df = pd.DataFrame(data)# Using 'Address' as the column name and equating it to the list df2 = df.assign(address = [ 'Delhi' , 'Bangalore' , 'Chennai' , 'Patna' ])# Observe the result df2

输出如下：

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方法4：通过使用字典
我们可以使用Python字典在pandas DataFrame中添加新列。使用现有列作为键值, 它们各自的值将是新列的值。

# Import pandas package import pandas as pd# Define a dictionary containing Students data data = https://www.lsbin.com/{'Name' : [ 'Jai' , 'Princi' , 'Gaurav' , 'Anuj' ], 'Height' : [ 5.1 , 6.2 , 5.1 , 5.2 ], 'Qualification' : [ 'Msc' , 'MA' , 'Msc' , 'Msc' ]}# Define a dictionary with key values of # an existing column and their respective # value pairs as the # values for our new column. address = { 'Delhi' : 'Jai' , 'Bangalore' : 'Princi' , 'Patna' : 'Gaurav' , 'Chennai' : 'Anuj' }# Convert the dictionary into DataFrame df = pd.DataFrame(data)# Provide 'Address' as the column name df[ 'Address' ] = address# Observe the output df

输出如下：