The row heading is get sorted, to avoid the first row should be skipped. This is can be done by using the command "next( )".

The default is reading in text mode. In this mode, while reading from the file the data would be in the format of strings.

Write mode:
Open a file for writing. Creates a new file if it does not exist or truncates the file if it exists.
Append mode:
Open for appending at the end of the file without truncating it. Creates a new file if it does not exist.

Program: To read a csv file with comma (,)
#importing csv
import csv
#opening the csv file which is in different location with read mode
with open('c:\\Pyprg\ \sample1.csv', 'r') as F:
#other way to open the file is
f=('C:\\pyprg\\sample1.csv', 'r')
reader = csv.reader(F))
#printing each line of the Data row by row.
print (row)
F. close( )
Output:
['SNO','NAME', 'CITY']
['12101', 'RAM', 'CHENNAI']
['12102', 'LAVANYA' "TIRUCHY']
['12103', 'LAKSHMAN', 'MADURAI']

Program: To modify an existing file
import csv
row = ['3: 'Meena','Bangalore']
with open('Student.csv', 'r') as read file:
reader = csv.reader (read File)
lines = list (reader) 
lines [3] = row
with open ('Student.csv', 'w') as write file:
# returns the writer object which converts the user data with delimiter.
writer = csv.writer(writefile)
#writerows() method writes multiple rows to a csv file
writer. writerows(lines)
readFile.close()
writeFile.close()
Output:

Rules to be followed to format data in a CSV file:
(i) Each record (row of data) is to be located on a separate line, delimited by a line break by pressing enter key.
For example:↲
xxx,yyy↲
↲denotes enter Key to be pressed
(ii) The last record in the file mayor may not have an ending line break.
For example:
ppp, qqq↲
yyy, xxx
(iii) There may be an optional header line appearing as the first line of the file with the same format as normal record lines. The header will contain names corresponding to the fields in the file and should contain the same number of fields as the records in the rest of the file.
For example:
field_name 1, field_name 2, field_name 3↲
aaa,bbb,ccc↲
zzz, yyy, xxx CRLF(Carriage Return and Line Feed)
(iv) Within the header and each record, there may be one or more fields, separated by commas. Spaces are considered part of a field and should not be ignored. The last field in the record must not be followed by a comma.
For example:
Red, Blue
(v) Each field mayor may not be enclosed in double quotes. If fields are not enclosed with double quotes, then double quotes may not appear inside the fields
For example:
"Red","Blue","Green"↲  
Black, White, Yellow 
(vi) Fields containing line breaks (CRLF), double quotes, and commas should be enclosed in double-quotes.
For example:
Red, ",", Blue CRLF 
Red, Blue, Green
(vii) If double-quotes are used to enclose fields, then a double-quote appearing inside a field must be preceded with another double quote.
For example:
"Red, " "Blue", "Green",
White

We can write the csv file with quotes, by registering new dialects using csv.register_dialect() class of csv module.
Program:
import csv
info = [['SNO: 'Person: 'DOB'],
['1', 'Madhu,' '18/12/2001'],
['2', 'Sowmya', '19/2/1998'],
['3', 'Sangeetha', '20/3/1999'],
['4', 'Eshwar', '21/4/2000'],
['5', 'Anand', '22/5/2001']]
csv.register_dialect('MyDialect',quoting=csv.QUOTE_ALL)
with open('c:\\pyprg\\ch13\\person.csv', 'w') as f:
writer = csv.writer(f, dialect='myDialect')
for row in info:
writer. writerow(row)
f.close()
Output
file: "Person.csv"
"SNO","Person", "DOB", "1", "Madhu", "18/12/2001"
"2, "Sowmya", "19/2/1998", "3", "Sangeetha",
"20/3/1999", "4", "Eshwar", "21/4/2000"
"5", "Anand", "22/5/2001".