To the existing dataframe, lets add new column named “Total_score” using by adding “Score1” and “Score2” using apply() function as shown below #### new columns based on existing columns df['Total_Score'] = df.apply(lambda row: row.Score1 + row.Score2, axis = 1) df Add a new column in pandas python using existing column. Output: Method #4: By using a dictionary We can use a Python dictionary to add a new column in pandas DataFrame. I have a csv file which is usually has between 100 and 200 columns. Code faster with the Kite plugin for your code editor, featuring Line-of-Code Completions and cloudless processing. Python: Add a column to an existing CSV file; Python: How to unzip a file | Extract Single, multiple or all files from a ZIP archive I am trying to add a new row to my old csv file. I have a new column of data that I want to add to the csv file. it should look like this: id, header1, header2, header1_1, header1_2, header1_3 not new columns. The column has no name, and i have problem to add the column name, already tried reindex, pd.melt, rename, etc. Right now this code will write three columns of data: I am new to python and I have a csv file of the following type id, header1, header2 1, 80-80-20, a 2, 30,b 3,,c 4,60-20,d Now I would like to separate the values in header1 to new columns where the -is the "delimiter", i.e. Python: How to create a zip archive from multiple files or Directory; Python : How to remove a file if exists and handle errors | os.remove() | os.ulink() Python: How to append a new row to an existing csv file? If not, check that post out! Use an existing column as the key values and their respective values will be the values for new column. Open ‘input.csv’ file in read mode and create csv.reader object for this csv file. Check out the newer post, about this topic, to learn more about converting columns in Python. DataFrame.assign(**kwargs) It accepts a keyword & value pairs, where a keyword is column name and value is either list / … Wanted to know are there any better ways of doing this. If you want that cell value doesn't gets copy, so first of all create a empty Column in your csv file manually, like you named it as Hours then, Now for this you can add this line in above code, csv_input['New Value'] = csv_input['Hours'] or simply we can, without adding the manual column, we can. In Python, Pandas Library provides a function to add columns i.e. Kite is a free autocomplete for Python developers. After reading your data from a CSV file, renaming the column, and adding a new column, you also may need to change your data types to numeric. csv_input['New Value'] = '' #simple and easy Python: Add a column to an existing CSV file – thispointer.com, If using pandas is an option: import pandas as pd df = pd.read_csv('filename.csv') new_column = pd.DataFrame({'new_header': Add a column with same values to an existing CSV file. Append a Column to Pandas Dataframe Example 2: How do I add a new column to an already existing csv file and add unique values to each line of the new column for the length of the csv file? Basically, it gets updated each time I run the Python script. Right now I am storing the old csv rows values in a list and then deleting the csv file and creating it again with the new list value. 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