Python for Beginners: Pandas Insert Columns into a DataFrame in Python :
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We use a pandas dataframe to store and manipulate tabular data in python. In this article, we will discuss how to insert a new column into the pandas dataframe using the insert() method.
The Pandas insert() Method
The insert() method is used to insert a column into a dataframe at a specific position. It has the following syntax.
DataFrame.insert(loc, column, value, allow_duplicates=_NoDefault.no_default)Here,
- The
locparameter takes the index at which the new column is inserted as its input argument. - The
columnparameter takes the column name as its input. - The
valueparameter takes a list or pandas series as values for the specified column. - The
allow_duplicatesparameter is used to decide if we can insert duplicate column names into the dataframe. By default, theinsert()method raises a ValueError exception if the dataframe contains a column with the same name that we are trying to insert. If you want to insert duplicate column names into the pandas dataframe, you can set theallow_duplicatesparameter to True.
Pandas Insert a Column at The Beginning of a DataFrame
To insert a column at the beginning of a dataframe, we can use the insert() method. Here, we will set the loc parameter to 0 so that the new column is inserted at the beginning. You can observe this in the following example.
import pandas as pd
myDicts=[{"Roll":1,"Maths":100, "Physics":80, "Chemistry": 90},
{"Roll":2,"Maths":80, "Physics":100, "Chemistry": 90},
{"Roll":3,"Maths":90, "Physics":80, "Chemistry": 70},
{"Roll":4,"Maths":100, "Physics":100, "Chemistry": 90},
{"Roll":5,"Maths":90, "Physics":90, "Chemistry": 80},
{"Roll":6,"Maths":80, "Physics":70, "Chemistry": 70}]
df=pd.DataFrame(myDicts)
print("The original dataframe is:")
print(df)
df.insert(0,"Name", ["Aditya","Joel", "Sam", "Chris", "Riya", "Anne"])
print("The mofified dataframe is:")
print(df)Output:
The original dataframe is:
Roll Maths Physics Chemistry
0 1 100 80 90
1 2 80 100 90
2 3 90 80 70
3 4 100 100 90
4 5 90 90 80
5 6 80 70 70
The mofified dataframe is:
Name Roll Maths Physics Chemistry
0 Aditya 1 100 80 90
1 Joel 2 80 100 90
2 Sam 3 90 80 70
3 Chris 4 100 100 90
4 Riya 5 90 90 80
5 Anne 6 80 70 70In this example, we first converted a list of dictionaries to a dataframe using the DataFrame() function. Then, we inserted the Name column in the created dataframe at index 0 using the insert() method. For this, we passed the value 0 as the first input argument, the string "Name" as the second input argument and the list of values as the third input argument to the insert() method.
Insert Column at The End of a DataFrame in Python
To insert a column at the end of the dataframe, we can directly assign the column values to the column name in the dataframe as shown below.
import pandas as pd
myDicts=[{"Roll":1,"Maths":100, "Physics":80, "Chemistry": 90},
{"Roll":2,"Maths":80, "Physics":100, "Chemistry": 90},
{"Roll":3,"Maths":90, "Physics":80, "Chemistry": 70},
{"Roll":4,"Maths":100, "Physics":100, "Chemistry": 90},
{"Roll":5,"Maths":90, "Physics":90, "Chemistry": 80},
{"Roll":6,"Maths":80, "Physics":70, "Chemistry": 70}]
df=pd.DataFrame(myDicts)
print("The original dataframe is:")
print(df)
df["Name"]= ["Aditya","Joel", "Sam", "Chris", "Riya", "Anne"]
print("The mofified dataframe is:")
print(df)Output:
The original dataframe is:
Roll Maths Physics Chemistry
0 1 100 80 90
1 2 80 100 90
2 3 90 80 70
3 4 100 100 90
4 5 90 90 80
5 6 80 70 70
The mofified dataframe is:
Roll Maths Physics Chemistry Name
0 1 100 80 90 Aditya
1 2 80 100 90 Joel
2 3 90 80 70 Sam
3 4 100 100 90 Chris
4 5 90 90 80 Riya
5 6 80 70 70 AnneIn the above example, we have used the indexing operator to insert a new column at the end of a dataframe.
Instead of the above approach, we can also use the insert() method to insert a column at the end. For this, we will use the following steps.
- First, will obtain the list of column names using the
columnsattribute of the dataframe. Thecolumnsattribute contains a list of column names. - Next, we will use the
len()function to find the total number of columns in the dataframe. Let it benumCol. - Once, we get the number of columns in the dataframe, we know that the current columns exist at the positions 0 to
numCol-1. Hence, we will insert the new column to the dataframe at the indexnumColusing theinsert()method.
After execution of the above steps, we can insert a column at the end of the dataframe as shown in the following example.
import pandas as pd
myDicts=[{"Roll":1,"Maths":100, "Physics":80, "Chemistry": 90},
{"Roll":2,"Maths":80, "Physics":100, "Chemistry": 90},
{"Roll":3,"Maths":90, "Physics":80, "Chemistry": 70},
{"Roll":4,"Maths":100, "Physics":100, "Chemistry": 90},
{"Roll":5,"Maths":90, "Physics":90, "Chemistry": 80},
{"Roll":6,"Maths":80, "Physics":70, "Chemistry": 70}]
df=pd.DataFrame(myDicts)
print("The original dataframe is:")
print(df)
numCol=len(df.columns)
df.insert(numCol,"Name", ["Aditya","Joel", "Sam", "Chris", "Riya", "Anne"])
print("The mofified dataframe is:")
print(df)Output:
The original dataframe is:
Roll Maths Physics Chemistry
0 1 100 80 90
1 2 80 100 90
2 3 90 80 70
3 4 100 100 90
4 5 90 90 80
5 6 80 70 70
The mofified dataframe is:
Roll Maths Physics Chemistry Name
0 1 100 80 90 Aditya
1 2 80 100 90 Joel
2 3 90 80 70 Sam
3 4 100 100 90 Chris
4 5 90 90 80 Riya
5 6 80 70 70 AnnePandas Insert Column at a Specific Index in a DataFrame
To insert a column at a specific position in the dataframe, you can use the insert() method as shown below.
import pandas as pd
myDicts=[{"Roll":1,"Maths":100, "Physics":80, "Chemistry": 90},
{"Roll":2,"Maths":80, "Physics":100, "Chemistry": 90},
{"Roll":3,"Maths":90, "Physics":80, "Chemistry": 70},
{"Roll":4,"Maths":100, "Physics":100, "Chemistry": 90},
{"Roll":5,"Maths":90, "Physics":90, "Chemistry": 80},
{"Roll":6,"Maths":80, "Physics":70, "Chemistry": 70}]
df=pd.DataFrame(myDicts)
print("The original dataframe is:")
print(df)
df.insert(2,"Name", ["Aditya","Joel", "Sam", "Chris", "Riya", "Anne"])
print("The mofified dataframe is:")
print(df)Output:
The original dataframe is:
Roll Maths Physics Chemistry
0 1 100 80 90
1 2 80 100 90
2 3 90 80 70
3 4 100 100 90
4 5 90 90 80
5 6 80 70 70
The mofified dataframe is:
Roll Maths Name Physics Chemistry
0 1 100 Aditya 80 90
1 2 80 Joel 100 90
2 3 90 Sam 80 70
3 4 100 Chris 100 90
4 5 90 Riya 90 80
5 6 80 Anne 70 70In this example, we have inserted the Name column at index 2 of the input dataframe using the insert() method.
Conclusion
In this article, we discussed different ways to insert a column in a pandas dataframe. To learn more about python programming, you can read this article on how to create an empty dataframe in python. You might also like this article on working with XML files in Python.
I hope you enjoyed reading this article. Stay tuned for more informative articles.
Happy Learning!
The post Pandas Insert Columns into a DataFrame in Python appeared first on PythonForBeginners.com.
March 06, 2023 at 07:30PM
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