Computer Science : Database concepts and MySql : Python and CSV Files
Points to remember:
· A CSV file is a human readable text file where each line has a number of fields, separated by commas or some other delimiter
· Excel is a binary file whereas CSV format is a plain text format
· The two ways to read a CSV file are using csv.reader() function and using DictReader class.
· The default mode of csv file in reading and writing is text mode
· Binary mode can be be used when dealing with non-text files like image or exe files.
· Python has a garbage collector to clean up unreferenced objects
· close() method will free up the resources that were tied with the file
· By default CSV files should open automatically in Excel
· The CSV library contains objects and other code to read, write, and process data from and to CSV files.
· “skipinitialspace” is used for removing whitespaces after the delimiter
· To sort by more than one column operator.itemgetter() can be used
· DictReader() class of csv module creates an object which maps data to a dictionary
· CSV file having custom delimiter is read with the help of csv.register_dialect().
· To sort by more than one column itemgetter() with multiple indices is used.
· csv.reader and csv.writer work with list/tuple, while csv.DictReader and csv.DictWriter work with dictionary .
· csv.DictReader and csv.DictWriter take additional argument fieldnames that are used as dictionary keys.
· The function dict() is used to print the data in dictionary format without order.
· The csv.writer() method returns a writer object which converts the user’s data into delimited strings.
· The writerow() method writes one row at a time. Writerows() method is used to write all the data at once
· Adding a new row at the end of the file is called appending a row.