1. CSV File Manipulation

2. Structured Text Files
Simple text files are a collection of lines with an escape sequence at the end of each line.
There is no definitive way to identify specific pieces of information unless there is a specified format to the file.
Ex. /etc/passwd
username:*:UID:GID: name: home Path: shell
However there are several structured files
Tab Delimited – values separated with a tab
CSV – values separated with a ‘,’
HTML/XML – tags , ‘< >’

3. Comma Separated Values
Delimited files are a common format often used as an exchange format for spreadsheets and databases.
Each line in a CSV file represents a row in the spreadhseet
Usually there is a header that denoted each of the column names.
Since CSV’s are a formatted text file they can still have end of line escape sequences
CSV vs escel and otherspreadsheets
No types – all strings
No fonts, sizes or colors
No multiple worsheets
No cell widths or heights
No merged cells
No images or charts ID
Term
Course
Grade
201652
ISY150 A
CIS120 C
CIS150 F

4. Manipulating CSV Files vs. plain Text files
Since CSV files are just formatted text files the process to read them is similar to processing text files.
Create a file stream, create reader/writer object, process the reader/writer, close stream
When files are read in they need to be processed as lists(arrays) and each element is a unique element in the array that does not need to be split.
There is a unique module for processing csv files
Code: import csv

5. Read CSV Example
import csv exFile = open(‘example.csv’ , ‘r’) exReader = csv.reader(exFile) for row in exReader: print row exFile.close()
import csv
exFile = open(‘example.csv’ , ‘r’)
exReader = csv.reader(exFile)
exReader = list(exReader)
for i in (0, 10, 1):
print exReader[i]
exFile.close()

6. Write csv Example
import csv outFile = open(‘outputFile.csv’, ‘w’) outWriter = csv.writer(outFile) outWriter.writerow([‘Date’, ‘ID’, ‘GPA’]) outWriter.writerow([’01/12/2015’, ‘ ’, ‘3.0’]) outWriter.writerow([’01/12/2015’, ‘ ’, ‘2.64’]) outFile.close()

7. Process CSV Files in a directory example
import csv, os for currFile in os.listdir(‘~/Documents’) if (not currFile.endswith(‘.csv’)): continue else: # process csv file