Get column names from CSV using Python

CSV stands for Comma Separated Values and CSV files are essentially text files which are used to store data in a tabular fashion using commas (,) as delimiters. CSV is a file format and all the files of this format are stored with a .csv extension. It is a very popular and extensively used format for storing the data in a structured form. CSV files find a lot of applications in Machine Learning and Statistical Models. Python has a library dedicated to deal with operations catering to CSV files such as reading, writing, or modifying them. Following is an example of how a CSV file looks like.

This article deals with the different ways to get column names from CSV files using Python. The following approaches can be used to accomplish the same :

• Using Python’s CSV library to read the CSV file line and line and printing the header as the names of the columns
• Reading the CSV file as a dictionary using DictReader and then printing out the keys of the dictionary
• Converting the CSV file to a data frame using the Pandas library of Python

Method 1:

Using this approach, we first read the CSV file using the CSV library of Python and then output the first row which represents the column names.

Python3

# importing the csv library
import csv

# opening the csv file by specifying
# the location
# with the variable name as csv_file
with open('data.csv') as csv_file:

    # creating an object of csv reader
    # with the delimiter as ,
    csv_reader = csv.reader(csv_file, delimiter = ',')

    # list to store the names of columns
    list_of_column_names = []

    # loop to iterate through the rows of csv
    for row in csv_reader:

        # adding the first row
        list_of_column_names.append(row)

        # breaking the loop after the
        # first iteration itself
        break

# printing the result
print("List of column names : ",
      list_of_column_names[0])

Output:

List of column names : ['Column1', 'Column2', 'Column3']

Method 2:

Under the second approach, we use the DictReader function of the CSV library to read the CSV file as a dictionary. We can simply use keys() method to get the column names.

Steps :

• Open the CSV file using DictReader.
• Convert this file into a list.
• Convert the first row of the list to the dictionary.
• Call the keys() method of the dictionary and convert it into a list.
• Display the list.

Python3

# importing the csv library
import csv

# opening the csv file
with open('data.csv') as csv_file:

        # reading the csv file using DictReader
    csv_reader = csv.DictReader(csv_file)

    # converting the file to dictionary
    # by first converting to list
    # and then converting the list to dict
    dict_from_csv = dict(list(csv_reader)[0])

    # making a list from the keys of the dict
    list_of_column_names = list(dict_from_csv.keys())

    # displaying the list of column names
    print("List of column names : ",
          list_of_column_names)

Output :

List of column names : ['Column1', 'Column2', 'Column3']

Method 3: 

Under this approach, we read the CSV file as a data frame using the pandas library of Python. Then, we just call the column’s method of the data frame.

Python3

# importing the pandas library
import pandas as pd

# reading the csv file using read_csv
# storing the data frame in variable called df
df = pd.read_csv('data.csv')

# creating a list of column names by
# calling the .columns
list_of_column_names = list(df.columns)

# displaying the list of column names
print('List of column names : ',
      list_of_column_names)

Output :

List of column names : ['Column1', 'Column2', 'Column3']

The Data Frame looks as follows :

The CSV file as a Data Frame