Python Open File Error Handling
Contents |
you have probably seen some. There are (at least) two distinguishable kinds of errors: syntax errors and exceptions. 8.1. Syntax Errors¶ Syntax errors, also known as parsing errors, are perhaps the most common kind of complaint you python file io error handling get while you are still learning Python: >>> while True print 'Hello world' File python file open error handling "
Python File Handling Programs
how to handle them in Python programs. Most exceptions are not handled by programs, however, and result in error messages as shown here: >>> 10 * (1/0) Traceback (most recent call last): File "
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company
Python Error Handling Best Practices
Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs python try except catch all errors Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, file handling in c++ just like you, helping each other. Join them; it only takes a minute: Sign up What is a good way to handle exceptions when trying to read a file in python? up vote 9 down vote favorite https://docs.python.org/2.7/tutorial/errors.html 2 I want to read a .csv file in python. I don't know if the file exists. My current solution is below. It feels sloppy to me because the two separate exception tests are awkwardly juxtaposed. Is there prettier way to do it? import csv fName = "aFile.csv" try: with open(fName, 'rb') as f: reader = csv.reader(f) for row in reader: pass #do stuff here except IOError: print "Could not read file:", fName python http://stackoverflow.com/questions/5627425/what-is-a-good-way-to-handle-exceptions-when-trying-to-read-a-file-in-python file-io exception-handling share|improve this question edited Apr 11 '11 at 21:08 asked Apr 11 '11 at 20:51 CharlesHolbrow 1,05431621 add a comment| 4 Answers 4 active oldest votes up vote 6 down vote accepted I guess I misunderstood what was being asked. Re-re-reading, it looks like Tim's answer is what you want. Let me just add this, however: if you want to catch an exception from open, then open has to be wrapped in a try. If the call to open is in the header of a with, then the with has to be in a try to catch the exception. There's no way around that. So the answer is either: "Tim's way" or "No, you're doing it correctly.". Previous unhelpful answer to which all the comments refer: import os if os.path.exists(fName): with open(fName, 'rb') as f: try: # do stuff except : # whatever reader errors you care about # handle error share|improve this answer edited Apr 11 '11 at 21:23 answered Apr 11 '11 at 20:55 Josh Caswell 52.6k11103152 5 Just because a file exists doesn't mean that you can read it! –Gabe Apr 11 '11 at 20:59 1 This isn't perfect, because it is possible that the file gets deleted (e.g. by another process) between checking that it exists and trying to open it. –Liqu
Python - Basic Syntax Python - Variable Types Python - Basic Operators Python - Decision Making Python - Loops Python - Numbers https://www.tutorialspoint.com/python/python_exceptions.htm Python - Strings Python - Lists Python - Tuples Python - http://www.greenteapress.com/thinkpython/thinkCSpy/html/chap11.html Dictionary Python - Date & Time Python - Functions Python - Modules Python - Files I/O Python - Exceptions Python Advanced Tutorial Python - Classes/Objects Python - Reg Expressions Python - CGI Programming Python - Database Access Python - Networking Python - Sending Email error handling Python - Multithreading Python - XML Processing Python - GUI Programming Python - Further Extensions Python Useful Resources Python - Questions and Answers Python - Quick Guide Python - Tools/Utilities Python - Useful Resources Python - Discussion Selected Reading Developer's Best Practices Questions and Answers Effective Resume Writing HR Interview Questions Computer Glossary Who is Who file handling in Python Exceptions Handling Advertisements Previous Page Next Page Python provides two very important features to handle any unexpected error in your Python programs and to add debugging capabilities in them − Exception Handling: This would be covered in this tutorial. Here is a list standard Exceptions available in Python: Standard Exceptions. Assertions: This would be covered in Assertions in Python tutorial. List of Standard Exceptions − EXCEPTION NAME DESCRIPTION Exception Base class for all exceptions StopIteration Raised when the next() method of an iterator does not point to any object. SystemExit Raised by the sys.exit() function. StandardError Base class for all built-in exceptions except StopIteration and SystemExit. ArithmeticError Base class for all errors that occur for numeric calculation. OverflowError Raised when a calculation exceeds maximum limit for a numeric type. FloatingPointError Raised when a floating point calculation fails. ZeroDivisonError Raised when division or modulo by zero takes place for all numeric types. AssertionError Raised in case of failure of the Assert statement. Att
exceptions While a program is running, its data is in memory. When the program ends, or the computer shuts down, data in memory disappears. To store data permanently, you have to put it in a file. Files are usually stored on a hard drive, floppy drive, or CD-ROM. When there are a large number of files, they are often organized into directories (also called "folders"). Each file is identified by a unique name, or a combination of a file name and a directory name. By reading and writing files, programs can exchange information with each other and generate printable formats like PDF. Working with files is a lot like working with books. To use a book, you have to open it. When you're done, you have to close it. While the book is open, you can either write in it or read from it. In either case, you know where you are in the book. Most of the time, you read the whole book in its natural order, but you can also skip around. All of this applies to files as well. To open a file, you specify its name and indicate whether you want to read or write. Opening a file creates a file object. In this example, the variable f refers to the new file object. >>> f = open("test.dat","w") >>> print f