File Open Error Handling Python
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 error handling python 3 of complaint you get while you are still learning Python: >>> while True print('Hello error handling in python script world') File "
Python Error Handling Loop
is detected at the function print(), since a colon (':') is missing before it. File name and line number are printed so you know where to look in case the input came from a script. 8.2. Exceptions¶ Even if a statement or expression is syntactically correct, it may cause an error when an attempt is made to execute it. Errors detected during execution are called exceptions and are not unconditionally python catch all errors fatal: you will soon learn 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 python error types about Stack Overflow the company Business Learn more about hiring developers or posting ads
Python Error Logging
with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow
Error Handling Perl
is a community of 4.7 million programmers, 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 https://docs.python.org/3/tutorial/errors.html a file in python? up vote 9 down vote favorite 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 http://stackoverflow.com/questions/5627425/what-is-a-good-way-to-handle-exceptions-when-trying-to-read-a-file-in-python in reader: pass #do stuff here except IOError: print "Could not read file:", fName python file-io exception-handling share|improve this question edited Apr 11 '11 at 21:08 asked Apr 11 '11 at 20:51 CharlesHolbrow 1,04931521 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 52.4k11103152 5 Just because a file exists doesn't mean that you can read it! –Gabe Apr 11 '11 at
Working with File Objects 6.2.1. Reading Files 6.2.2. Closing Files 6.2.3. Handling I/O Errors 6.2.4. Writing to Files 6.3. Iterating with for Loops 6.4. Using sys.modules 6.5. Working with Directories 6.6. Putting http://www.diveintopython.net/file_handling/ It All Together 6.7. Summary In this chapter, you will dive into exceptions, file objects, for loops, and the os and sys modules. If you've used exceptions in another programming language, you can skim the first section to get a sense of Python's syntax. Be sure to tune in again for file handling. 6.1.Handling Exceptions 6.1.1. Using Exceptions For Other Purposes Like many other programming languages, error handling Python has exception handling via try...except blocks. Python uses try...except to handle exceptions and raise to generate them. Java and C++ use try...catch to handle exceptions, and throw to generate them. Exceptions are everywhere in Python. Virtually every module in the standard Python library uses them, and Python itself will raise them in a lot of different circumstances. You've already seen them repeatedly throughout this book. Accessing error handling python a non-existent dictionary key will raise a KeyError exception. Searching a list for a non-existent value will raise a ValueError exception. Calling a non-existent method will raise an AttributeError exception. Referencing a non-existent variable will raise a NameError exception. Mixing datatypes without coercion will raise a TypeError exception. In each of these cases, you were simply playing around in the Python IDE: an error occurred, the exception was printed (depending on your IDE, perhaps in an intentionally jarring shade of red), and that was that. This is called an unhandled exception. When the exception was raised, there was no code to explicitly notice it and deal with it, so it bubbled its way back to the default behavior built in to Python, which is to spit out some debugging information and give up. In the IDE, that's no big deal, but if that happened while your actual Python program was running, the entire program would come to a screeching halt. An exception doesn't need result in a complete program crash, though. Exceptions, when raised, can be handled. Sometimes an exception is really because you have a bug in your code (like accessing a variable that doesn't