I am implementing a simple logger in python.Find my code below, Sometimes it runs fine,at times I get ValueError at self.log('INFO','Append operation successful.')
Where am I doing wrong? I am new to python and have also referred to the doc. Unable to understand the inconsistency, also I am using python 3.9, tried using force parameter too. It is also not logging the level, like Critical, Info or Error.
import logging as logger
class data:
def __init__(self, filename,filetype,filesize,date):
self.filename=filename
self.filetype=filetype
self.filesize=filesize
self.date=date
def log(self,logtype,msg):
logger.basicConfig(filename="datalog.log",level=logger.INFO,force=True,format='%(asctime)s %(message)s')
if logtype == "INFO":
logger.info(msg)
elif logtype == "ERROR":
logger.ERROR(msg)
elif logtype == "CRITICAL":
logger.CRITICAL(msg)
else:
logger.info(msg)
def openFile(self):
try:
filename=self.filename+self.filetype
f=open(filename,'w+')
f.write("Hello, Lets learn OOPs in Python")
f.close()
self.log('INFO','Write operation successful.')
except Exception as e:
self.log('ERROR','Writing operation failed.')
def appendFile(self):
try:
f=open(self.filename+self.filetype,'a')
f.write("Appending some extra content")
f.close()
self.log('INFO','Append operation successful.')
except Exception as e:
self.log('ERROR','Append operation failed.')
sample = data('sample','.txt','1Mb','2021-08-20')
sample.appendFile()
sample.openFile()
Error:
ValueError: Unrecognised argument(s): force
During handling of the above exception, another exception occurred:
TypeError Traceback (most recent call last)
<ipython-input-1-e095529812fd> in log(self, logtype, msg)
12 logger.info(msg)
13 elif logtype == "ERROR":
---> 14 logger.ERROR(msg)
15 elif logtype == "CRITICAL":
16 logger.CRITICAL(msg)
TypeError: 'int' object is not callable
The force option to basicConfig is only available in Python 3.8+. Check your Python version.
Also, it's probably not a good idea to force reconfigure the logging system on each and every log event. Just configure it once, at the main entry point of your application.
Related
This is the code.
# mean_var_std.py
def calculate(list):
try:
if len(list) < 9:
raise ValueError
else:
return 0
except ValueError:
print("List must contain nine numbers.")
This is the test.
import unittest
import mean_var_std
# the test case
class UnitTests(unittest.TestCase):
def test_calculate_with_few_digits(self):
self.assertRaisesRegex(ValueError, "List must contain nine numbers.", mean_var_std.calculate, [2,6,2,8,4,0,1,])
if __name__ == "__main__":
unittest.main()
When I run it, I get the following output:
F
======================================================================
FAIL: test_calculate_with_few_digits (test_module.UnitTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/runner/fcc-mean-var-std-2/test_module.py", line 8, in test_calculate_with_few_digits
self.assertRaisesRegex(ValueError, "List must contain nine numbers.", mean_var_std.calculate, [2,6,2,8,4,0,1,])
AssertionError: ValueError not raised by calculate
----------------------------------------------------------------------
Ran 1 test in 0.001s
FAILED (failures=1)
The output says that the code isn't raising a ValueError, but from the code we can clearly see that the code raises a ValueError. Why is my code still failing the unittest?
It's because you catch the ValueError before the test can receive it.
Remove the try catch and it should work
# mean_var_std.py
def calculate(list):
if len(list) < 9:
print("List must contain nine numbers.")
raise ValueError
else:
return 0
I have a use case where I need to raise an exception and again throw the exception. For this I'm using raise keyword in both try and catch. The code is as below
try:
username = input ("username:")
If Len(username) != 6:
raise Exception
except Exception:
raise Exception ("username is not valid")
Is this the right way to do like this? Is it compliant to coding standards to raise Exception in both try and except blocks?
I'm guessing this is a simplified version of your actual use case, in which case it is generally correct. A couple of notes:
You can use raise without anything after it to re-raise the same error.
try:
raise ValueError('message')
except ValueError:
run_something()
raise # will raise ValueError ('message')
Don't raise a general Exception and don't catch them either, be specific, otherwise this code will obscure other errors and will be difficult to debug. If nothing else suits you, make an exception of your own:
class MyException(Exception):
pass
Then you can use it:
raise MyException('my message')
In your use case, if I understood it correctly, all of this together would be:
class InvalidUsername(Exception):
pass
try:
username = input('username: ')
if len(username) > 6:
raise InvalidUsername('Username is too long')
if '!' in username:
raise InvalidUsername('Invalid character in username')
except InvalidUsername:
handle_invalid_user()
raise
Example in the console:
>>> try:
... username = input('username: ')
... if len(username) > 6:
... raise InvalidUsername('Username is too long')
... if '!' in username:
... raise InvalidUsername('Invalid character in username')
... except InvalidUsername:
... handle_invalid_user()
... raise
...
username: test1234
Traceback (most recent call last):
File "<stdin>", line 4, in <module>
__main__.InvalidUsername: Username is too long
Or with an invalid character:
username: ofer!
Traceback (most recent call last):
File "<stdin>", line 6, in <module>
__main__.InvalidUsername: Invalid character in username
I was also looking to raise an exception when there is an error within the business logic from an external server and due to database connection.
I came across this arcticle to basically raise the exception especially when you are follwing an Controller-> Service -> Repository pattern.
https://flask.palletsprojects.com/en/2.1.x/errorhandling/
from flask import jsonify, request
class InvalidAPIUsage(Exception):
status_code = 400
def __init__(self, message, status_code=None, payload=None):
super().__init__()
self.message = message
if status_code is not None:
self.status_code = status_code
self.payload = payload
def to_dict(self):
rv = dict(self.payload or ())
rv['message'] = self.message
return rv
#app.errorhandler(InvalidAPIUsage)
def invalid_api_usage(e):
return jsonify(e.to_dict()), e.status_code
# an API app route for getting user information
# a correct request might be /api/user?user_id=420
#app.route("/api/user")
def user_api(user_id):
user_id = request.arg.get("user_id")
if not user_id:
raise InvalidAPIUsage("No user id provided!")
user = get_user(user_id=user_id)
if not user:
raise InvalidAPIUsage("No such user!", status_code=404)
return jsonify(user.to_dict())
[1]: https://flask.palletsprojects.com/en/2.1.x/errorhandling/
I hope this helps to developers who are developing enterprise level apps.
Say I have a function that can produce a vast variety of errors.
I have a ValueError that I need to catch, a specific AttributeError, and then I also need to handle any other type of error.
try:
func()
except AttributeError as e:
if "specific error text" in str(e):
print("The specific AttributeError occurred")
else:
raise
except ValueError:
print("A value error occurred")
except Exception as e:
print("Another error occurred: {}".format(str(e)))
Problem: If func() bubbles an AttributeError that's not the specific one I'm looking for, in this case, it'll be re-raised and not handled how I want it to be handled (via the general Exception handler).
How do I force non-specific errors to be handled further down in the chain, without duplicating code from the Exception section into the AttributeError section?
As an option you can process AttributeError and ValueError in one try-except block and all other Exceptions on the top level like
try:
try:
func()
except AttributeError as e:
if "specific error text" in str(e):
print("The specific AttributeError occurred")
else:
raise
except ValueError:
print("A value error occurred")
except Exception as e:
print("Another error occurred: {}".format(str(e)))
this may look a bit ugly though, so we can extract inner try-except block in a separate function like
def func_with_expected_exceptions_handling():
try:
func()
except AttributeError as e:
if "specific error text" in str(e):
print("The specific AttributeError occurred")
else:
raise
except ValueError:
print("A value error occurred")
and after that
try:
func_with_expected_exceptions_handling()
except Exception as e:
print("Another error occurred: {}".format(str(e)))
this doesn't save us from an actual nested structure, but it may come in handy if this kind of func processing arises in other places.
BTW, I don't think checking for a specific error message in exception is a good idea, we need a little bit more context to see if it can be done easier.
EDIT
If I understood correctly your func looks like
def func(...):
getattr(COMMANDS, cmd.command).command(irc_c, msg, cmd)
and you want to handle error from getattr call.
I can see next options here:
Wrap getattr call in try-except and process AttributeError in-place
def func(...):
try:
commander = getattr(COMMANDS, cmd.command)
except AttributeError:
print('Command {} not found'.format(cmd.command))
else:
commander.command(irc_c, msg, cmd)
Wrap getattr call in try-except, re-raise a custom exception (or ValueError) and process it afterwards in OP try-except
class CommandNotFound(Exception): pass
def func(...):
try:
commander = getattr(COMMANDS, cmd.command)
except AttributeError:
raise CommandNotFound() # or we can use `ValueError` instead
else:
commander.command(irc_c, msg, cmd)
Use default parameter of getattr function and make some kind of logging there like
class DefaultCommand:
def command(self, irc_c, msg, cmd):
print("Command {} is not found".format(cmd.command))
and after that used like
getattr(COMMANDS, cmd.command, DefaultCommand()).command(irc_c, msg, cmd)
Basically you need to handle the specific error first. From more general to more specific, i.e Exception => AttributeError => YourError
>>> try:
... raise MyCustomAttrErr("Hey, this failed!")
... except MyCustomAttrErr as e:
... print(e)
... except AttributteError as e:
... print("Attribute error raised")
... except Exception as e:
... print("Base exception raised")
...
Hey, this failed!
Python handled the except blocks in order from top to bottom and stops in the first block that captures it.
I have a dictionary that looks like this:
js = {'value': {'boot': {'delay': 0} } }
When I run the following command
print(js['value']['boot']['delay'])
I get 0 which is the behavior I expect to get.
When I run the following
print(js['value']['booooot']['delay'])
I get KeyError: 'booooot' which is also expected.
However, when I wrap all of this into a try/except and print the exception, I don't get the error as I expected.
def myfunc(js):
try:
js['value']['booooot']['delay']
except Exception as e:
print(e)
I just get the following at the console 'booooot'
Shouldn't I get KeyError: 'booooot' as I did when I ran the print outside of a try/except block?
import sys
def func(js):
try:
print(js['value']['boooot']['delay'])
except:
print("Error Information: " + str(sys.exc_info()))
js = {'value': {'boot': {'delay': 0} } }
func(js)
The command sys.exc_info() will return the exception information as a tuple, with index 0 being the error type and index 1 with the error itself.
The code above prints out
Error Information: (<class 'KeyError'>, KeyError('boooot'), <traceback object at 0x01867558>)
Thanks for asking! Hope this helps.
I'm a bit of a Python newbie and this is my first post to stackoverflow so please bear with me. :)
Before posting i have searched google and stackoverflow but cant seem to find anything similar to my issue.
I have a script that polls a website and retrieves the content.
It works fine for hours however if it encounters a socket timeout the script throws a typeerror even though I have an exception for it.
I'm sure I am missing something obvious, but cant put my finger on it.
Code:
timingout = 10
def get_url(url):
try:
sock = urllib.request.urlopen(url, timeout=timingout)
orig_html = sock.read()
html = orig_html.decode("utf-8", errors="ignore").encode('cp1252', errors='ignore')
sock.close()
except KeyboardInterrupt:
# Kill program if Control-C is pressed
sys.exit(0)
except urllib.error.URLError as e:
print("***Error= Page ", e.reason)
return
except timingout:
print("socket timed out - URL: %s", url)
else:
# See if site is Down or errors eg: 404
if html == None:
print ("page contains no content!?!")
return ''
# See if site is complaining
elif html == site_overload:
if _verbose:
print('ERROR: Too many requests - SLEEPING 600 secs')
time.sleep(600)
return ''
# If not, we are good
elif html:
return html
error:
return self._sock.recv_into(b)
**socket.timeout: timed out**
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "test.py", line 201, in <module>
main()
File "test.py", line 140, in main
http_text = get_text(site_id)
File "test.py", line 110, in get_text
return get_url(url)
File "test.py", line 59, in get_url
except timingout:
**TypeError: catching classes that do not inherit from BaseException is not allowed**
Thanks in advance for any suggestions & help!
It's caused by trying to use timingout to catch an exception. timingout is an integer object whereas the except statement only accepts objects inherited from the BaseException class.
Remove that except because it doesn't do anything. Also consider revising your try statement to only include a single operation. It will make troubleshooting easier and prevent you from having to break up your try statements later on when a bug occurs.