Exceptions in python

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Exceptions in python

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Exceptions in python

  1. 1. Disclaimer: This presentation is prepared by trainees of baabtra as a part of mentoring program. This is not official document of baabtra –Mentoring Partner Baabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt . Ltd
  2. 2. EXCEPTIONS IN PYTHON SHAMEENA.V shameenavayoli@gmail.com www.facebook.com/shamee na latheef twitter.com/shameena in.linkedin.com/in/shamean 9567135569
  3. 3. Introduction : Python uses exceptions to communicate errors and anomalies  exception is an object that indicates an error or anomalous condition code explicitly raise an exception by executing a raise statement.  If a program does not handle an exception, it terminates with an error traceback message
  4. 4. The try Statement • The try statement provides Python's exception-handling mechanism • It is a compound statement • It can take one of two different forms: 1) try clause followed by one or more except clauses 2) A try clause followed by exactly one finally clause
  5. 5. 1)try/except Syntax: try: statement(s) except [expression [, target]]: statement(s) [else: statement(s)]
  6. 6. Contd…. • The body of each except clause is known as an exception handler
  7. 7. 2) try/finally Syntax: try: statement(s) finally: statement(s) The finally clause establishes what is known as a clean-up handler
  8. 8. Example : f = open(someFile, "w") try: do_something_with_file(f) finally: f.close( )
  9. 9. Built-In Exception classes • BaseException mother of all exceptions • Exception : StandardError(base class for all built in exception) ArithmeticError FloatingPointError OverflowError ZeroDivisionError
  10. 10. AttributeError (On attribute reference or assignment failure ) EnvironmentError (On error outside Python) IOError OSError WindowsError ImportError (On failure of import to find module or name.) LookupError base class for IndexError, KeyError – IndexError On out-of-range sequence subscript - KeyError On reference to a non-existent mapping (dict) key
  11. 11. NameError UnBoundLocalError On reference to an unassigned local variable SyntaxError On parser encountering a syntax error – IndentationError On parser encountering an indentation syntax error --TabError On improper mixture of spaces and tabs
  12. 12. Example: try: con = psycopg2.connect(database='testdb', user='shafeequemonp' ) cur = con.cursor() print "Connecting to databasen ->%s" % (con) cur.execute("""INSERT INTO tbl_user(vchr_username) VALUES(%s)""",(ins_login_base.str_name)) con.commit() except psycopg2.DatabaseError, e: if con: con.rollback() print 'Error %s' % e sys.exit(1) finally: if con: con.close() return
  13. 13. THANKS
  14. 14. If this presentation helped you, please visit our page facebook.com/baabtra and like it. Thanks in advance. www.baabtra.com | www.massbaab.com |www.baabte.com
  15. 15. Contact Us Emarald Mall (Big Bazar Building) Mavoor Road, Kozhikode, Kerala, India. Ph: + 91 – 495 40 25 550 Start up Village Eranakulam, Kerala, India. Email: info@baabtra.com NC Complex, Near Bus Stand Mukkam, Kozhikode, Kerala, India. Ph: + 91 – 495 40 25 550

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