Python File Write Error Handling
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Python Raise Custom Exception
Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up What syntax for generic except clause in python is a good way to handle exceptions when trying to read 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. python print exception 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 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
Is Nested Try Block Possible In Python
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. –Liquid_Fire Apr 11 '11 at 20:59 1 It's also possible that fName could be the name of some file which, even if it sticks around, cannot be opened for whatever reason — for example, if it is a directory or does not have permissions allowing it to be read by the executing process. –intuited Apr 11 '11 at 21:14 1 The "if exists(file): open(fi
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 python try except else complaint you get while you are still learning Python: >>> while True print('Hello world') File an exception can be in python "
Name Of Errors In Python
pointing at the earliest point in the line where the error was detected. The error is caused by (or at least detected at) the token preceding the arrow: in the example, the error is detected at the http://stackoverflow.com/questions/5627425/what-is-a-good-way-to-handle-exceptions-when-trying-to-read-a-file-in-python 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 fatal: you will soon learn https://docs.python.org/3/tutorial/errors.html 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 "
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generic Exception. Use user-defined exceptions for application-level errors. Update, 2016-02-26 The kind folks at Webucator made a video based on this post. Check out the video at: https://youtu.be/T94vZmOZodY and other Webucator Online Python Classes. Disclaimer: I’m not a python fan (and certainly not an expert). Comments, feedback, suggestions and improvements are welcomed. without catching exceptions This typical python code: #!/usr/bin/env python import sys a = open("/non/existing/file","r") Will result in this output: $ ./bad0.py Traceback (most recent call last): File "./bad0.py", line 3, in