Tamilnadu Samacheer Kalvi 12th Computer Science Notes Chapter 13 Python and CSV Files Notes

CSV file:
A CSV file is a human readable text file where each line has a number of fields, separated by commas or some other delimiter

Two ways to read a CSV file:
The two ways to read a CSV file are using csv.reader() function and using DictReader class.

Python File Modes:



‘r’ Open a file for reading, (default)
‘w’ Open a file for writing. Creates a new file if it does not exist or truncates the file if it exists.
‘x’ Open a file for exclusive creation. If the file already exists, the operation fails.
‘a’ Open for appending at the end of the file without truncating it. Creates a new file if it does not exist.
‘t’ Open in text mode, (default)
‘b’ Open in binary mode.
‘+’ Open a file for updating (reading and writing)
  • The default mode of csv file in reading and writing is text mode
  • Binary mode can be used when dealing with non-text files like image or exe files.

Garbage collector:
Python has a garbage collector to clean up unreferenced objects

Skip initial space:
“skip initial space” is used for removing whitespaces after the delimiter

CSV library:
The ŒV library contains objects and other code to read, write, and process data from and to CSV files.

csv.reader, csv.writer,csv.ÐictReader, csv.DictWriter:

  • csv.reader and csv.writer work with list/tuple.
  • csv.DictReader and csv.Dict Writer work with dictionary.
  • csv.DictReader and csv.Dict Writer take additional arguments fieldnames that are used as dictionary keyš.
  • The csv.writer() method returns a writet object which converts the user’s data into delimited strings.
  • DictReader() class of csv module creates an object which maps data to a dictionary.

operator.itemgetter can be used to sort by more than one column operator.itemgetter()

itemgetter() with multiple indices is used to sort by more than one column.

writerow() Vs Writerows():
The writerowQ method writes one row at a time. WriterowsQ method is used to write all the data at once.

CSV file having custom delimiter is read with the help of csv.register_dialect().

close() method:
close() method will free up the resources that were tied with the file

Line Terminator:
A Line Terminator is a string used to terminate lines produced by writer.

A dialect is a class of csv module which helps to define parameters for reading and writing CSV.

Ordered Diet:
An Ordered Diet is a dictionary subclass which saves the order in which its contents are added.

Samacheer Kalvi 12th Computer Science Notes