How to Add New column in DataFrame
We can easily add a new column in the existing DataFrame. The following examples will clear you, on how to add new column in DataFrame.
#1. Method :- By adding a new list or Series
import pandas as pd
data = { ‘first’ : pd.Series ( [ 1, 2, 3 ] , index= [‘a’, ‘b’, ‘c’ ] ),
‘second’ : pd.Series ( [ 10, 20, 30 ], index= [‘a’, ‘b’, ‘c’ ] ) }
df= pd.DataFrame(data)
print (df)
print (“After adding a new column in Data Frame “)
df [ ‘third’ ]= pd.Series( [ 11, 22, 33 ], index= [‘a’, ‘b’, ‘c’ ] )
print (df)
Its output will be
first second
一一一一一一一一一
a 1 10
b 2 20
c 3 30
After adding a new column in Data Frame
first second third
一一一一一一一一一一一一
a 1 10 11
b 2 20 22
c 3 30 33
Note:- You can see it’s very easy to add a new column in DataFrame, You can add columns as much you want.
#2. Method :- By using DataFrame.insert() function
This method provides freedom to add a new column at any position, not just at the end.
import pandas as pd
data = { ‘first’ : pd.Series ( [ 1, 2, 3 ] , index= [‘a’, ‘b’, ‘c’ ] ),
‘second’ : pd.Series ( [ 10, 20, 30 ], index= [‘a’, ‘b’, ‘c’ ] ) }
df= pd.DataFrame(data)
print (df)
print (“By using insert() addition of a new column in Data Frame “)
df.insert(1, “third ” , [ 11, 22, 33 ], True )
print (df)
Its output will be
first second
一一一一一一一一一
a 1 10
b 2 20
c 3 30
By using insert() addition of a new column in Data Frame
first third second
一一一一一一一一一一一一
a 1 11 10
b 2 22 20
c 3 33 30
Note:- By using insert(), we can add a new column in DataFrame at any position, not just at the end.
#3. Method :- By using DataFrame.assign() function
When we add a new column by using this method it will create a new DataFrame with a new column added to the old DataFrame.
import pandas as pd
data = { ‘first’ : pd.Series ( [ 1, 2, 3 ] , index= [‘a’, ‘b’, ‘c’ ] ),
‘second’ : pd.Series ( [ 10, 20, 30 ], index= [‘a’, ‘b’, ‘c’ ] ) }
df= pd.DataFrame(data)
print (df)
print (“To add a new column by using assign() it will create a new Data Frame “)
df2= df.assign(third = [ 11, 22, 33 ] )
print (df2)
Its output will be
first second
一一一一一一一一一
a 1 10
b 2 20
c 3 30
To add a new column by using assing() it will create a new DataFrame
first second third
一一一一一一一一一一一一
a 1 10 11
b 2 20 22
c 3 30 33
Note:- When we use assign(), to add a new column in Data Frame it will create a new DataFrame.
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