how to read a CSV file line by line with or without header in python

                                    #Read a CSV file line by line using csv module DictReader object

#Suppose we have a csv file students.csv and its contents are,
Id,Name,Course,City,Session
21,Mark,Python,London,Morning
22,John,Python,Tokyo,Evening
23,Sam,Python,Paris,Morning
32,Shaun,Java,Tokyo,Morning

#With csv module’s DictReader class object we can iterate over the lines of a csv file as a dictionary i.e.
#for each row a dictionary is returned, which contains the pair of column names and cell values for that row.
#Let’s understand with an example,

from csv import DictReader
# open file in read mode
with open('students.csv', 'r') as read_obj:
    # pass the file object to DictReader() to get the DictReader object
    csv_dict_reader = DictReader(read_obj)
    # iterate over each line as a ordered dictionary
    for row in csv_dict_reader:
        # row variable is a dictionary that represents a row in csv
        print(row)

Output:
{'Id': '21', 'Name': 'Mark', 'Course': 'Python', 'City': 'London', 'Session': 'Morning'}
{'Id': '22', 'Name': 'John', 'Course': 'Python', 'City': 'Tokyo', 'Session': 'Evening'}
{'Id': '23', 'Name': 'Sam', 'Course': 'Python', 'City': 'Paris', 'Session': 'Morning'}
{'Id': '32', 'Name': 'Shaun', 'Course': 'Java', 'City': 'Tokyo', 'Session': 'Morning'}

                                    #Get column names from header in csv file

#Suppose we have a csv file students.csv and its contents are,
Id,Name,Course,City,Session
21,Mark,Python,London,Morning
22,John,Python,Tokyo,Evening
23,Sam,Python,Paris,Morning
32,Shaun,Java,Tokyo,Morning

#DictReader class has a member function that returns the column names of the csv file as list.
#let’s see how to use it,

from csv import DictReader
# open file in read mode
with open('students.csv', 'r') as read_obj:
    # pass the file object to DictReader() to get the DictReader object
    csv_dict_reader = DictReader(read_obj)
    # get column names from a csv file
    column_names = csv_dict_reader.fieldnames
    print(column_names)

Output:
['Id', 'Name', 'Course', 'City', 'Session']

                                    #Read a CSV file without header

#Suppose we have a csv file students.csv and its contents are,
Id,Name,Course,City,Session
21,Mark,Python,London,Morning
22,John,Python,Tokyo,Evening
23,Sam,Python,Paris,Morning
32,Shaun,Java,Tokyo,Morning

#In the previous example we iterated through all the rows of csv file including header. But suppose we want to skip the header and iterate over the remaining rows of csv file.
#Let’s see how to do that,

from csv import reader
# skip first line i.e. read header first and then iterate over each row od csv as a list
with open('students.csv', 'r') as read_obj:
    csv_reader = reader(read_obj)
    header = next(csv_reader)
    # Check file as empty
    if header != None:
        # Iterate over each row after the header in the csv
        for row in csv_reader:
            # row variable is a list that represents a row in csv
            print(row)

Output:
['21', 'Mark', 'Python', 'London', 'Morning']
['22', 'John', 'Python', 'Tokyo', 'Evening']
['23', 'Sam', 'Python', 'Paris', 'Morning']
['32', 'Shaun', 'Java', 'Tokyo', 'Morning']
Header was: 
['Id', 'Name', 'Course', 'City', 'Session']

                                    #Read specific columns from a csv file while iterating line by line

#Suppose we have a csv file students.csv and its contents are,
Id,Name,Course,City,Session
21,Mark,Python,London,Morning
22,John,Python,Tokyo,Evening
23,Sam,Python,Paris,Morning
32,Shaun,Java,Tokyo,Morning


#Read specific columns (by column name) in a csv file while iterating row by row


#Iterate over all the rows of students.csv file line by line, but print only two columns of for each row,

from csv import DictReader
# iterate over each line as a ordered dictionary and print only few column by column name
with open('students.csv', 'r') as read_obj:
    csv_dict_reader = DictReader(read_obj)
    for row in csv_dict_reader:
        print(row['Id'], row['Name'])

Output:
21 Mark
22 John
23 Sam
32 Shaun


#Read specific columns (by column Number) in a csv file while iterating row by row


#Iterate over all rows students.csv and for each row print contents of 2ns and 3rd column,

from csv import reader
# iterate over each line as a ordered dictionary and print only few column by column Number
with open('students.csv', 'r') as read_obj:
    csv_reader = reader(read_obj)
    for row in csv_reader:
        print(row[1], row[2])

Output:
Name Course
Mark Python
John Python
Sam Python
Shaun Java