When throwing an exception how do I get the compiler to throw my custom exception AND the compiler exception.
Here is an example of what I want to happen
def func_A(int)
try:
ans = 1 + int
print(ans)
except:
print('Oops your input was wrong')
def func_B(int)
ans = 1 + int
print(ans)
Input_A:
func_A('Hello_World')
Output_A:
'Oops your input was wrong'
Input_B:
func_B('Hello_World')
Output_B:
File "<ipython-input-5-fe7d28575c18>", line 2
def func_B(int)
^
SyntaxError: invalid syntax
Desired Output:
'Oops your input was wrong'
File "<ipython-input-5-fe7d28575c18>", line 2
def func_B(int)
^
SyntaxError: invalid syntax
Try adding a raise to the end of your except to raise the exception again, like this:
def func_A(int):
try:
ans = 1 + int
print(ans)
except:
print('Oops your input was wrong')
raise
func_A('Hello_World')
Output:
Oops your input was wrong
Traceback (most recent call last):
File "/home/ashish/s.py", line 15, in <module>
func_A('Hello_World')
File "/home/ashish/s.py", line 3, in func_A
ans = 1 + int
TypeError: unsupported operand type(s) for +: 'int' and 'str'
Related
I want to print an error's line number and error message in a nicely displayed way. The follow is my code, which uses linecache:
import linecache
def func():
if xx == 1:
print('ok')
try:
func()
except:
exc_type, exc_obj, tb = sys.exc_info()
f = tb.tb_frame
lineno = tb.tb_lineno
filename = f.f_code.co_filename
linecache.checkcache(filename)
line = linecache.getline(filename, lineno, f.f_globals)
print_('ERROR - (LINE {} "{}"): {}'.format(lineno, line.strip(), exc_obj))
However, this only gives where the func() is called:
ERROR - (LINE 8 ""): name 'xx' is not defined
Is there a way to print the line number where the error actually occured, which should be Line 4? Or even better, can I print Line 8 and then trace back to line 4? For example, if I do not use try - except, the code:
def func():
if xx == 1:
print('ok')
func()
will give me the following error message, which is much better to locate the error:
File "<input>", line 5, in <module>
File "<input>", line 2, in func
NameError: name 'xx' is not defined. Did you mean: 'xxx'?
You can use traceback and sys modules to get advanced traceback output like you are wishing for.
Here is an example:
import traceback
import sys
def func():
zeroDivide = 1 / 0
try:
func()
except Exception:
print(traceback.format_exc()) # This line is for getting traceback.
print(sys.exc_info()[2]) # This line is getting for the error type.
Output will be:
Traceback (most recent call last):
File "b:\abc\1234\pppp\main.py", line 10, in <module>
func()
File "b:\abc\1234\pppp\main.py", line 7, in func
zeroDivide = 1 / 0
ZeroDivisionError: division by zero
You can use the traceback module to get the line number of the error,
import traceback
def function():
try:
# code
except:
tb_list = traceback.extract_tb(sys.exc_info()[2])
line_number = tb_list[-1][1]
print("An error occurred on line:", line_number)
You can use the traceback.extract_tb() function. This function returns a list of traceback objects, each of which contain information about the stack trace. The last element of this list, tb_list[-1], holds information about the line where the exception occurred. To access the line number, you can use the second element of this tuple, tb_list[-1][1]. This value can then be printed using the print() function.
To get the line number as an int you can get the traceback as a list from traceback.extract_tb(). Looking at the last item gives you the line where the exception was raised:
#soPrintLineOfError2
import sys
import traceback
def func():
if xx == 1:
print('ok')
try:
func()
except Exception as e:
tb = sys.exc_info()[2]
ss = traceback.extract_tb(tb)
ss1 = ss[-1]
print(ss1.line)
print(ss1.lineno)
Output:
if xx == 1:
6
I cannot figure out a problem I am having with code written in Python 2.7. I am converting the references to ints, but I keep getting a type exception bad operand type for unary +: 'str'. Can anyone assist?
import urllib2
import time
import datetime
stocksToPull = 'EBAY', 'AAPL'
def pullData(stock):
try:
print 'Currently pulling', stock
print str(datetime.datetime.fromtimestamp(time.time()).strftime('%Y-%m-%d %H:%M:%S'))
urlToVisit = 'http://chartapi.finance.yahoo.com/instrument/1.0/' + \
stock + '/chartdata;type=quote;range=3y/csv'
saveFileLine = stock + '.txt'
try:
readExistingData = open(saveFileLine, 'r').read()
splitExisting = readExistingData.split('\n')
mostRecentLine = splitExisting[-2]
lastUnix = mostRecentLine.split(',')[0]
except Exception, e:
print str(e)
time.sleep(1)
lastUnix = 0
saveFile = open(saveFileLine, 'a')
sourceCode = urllib2.urlopen(urlToVisit).read()
splitSource = sourceCode.split('\n')
for eachLine in splitSource:
if 'values' not in eachLine:
splitLine = eachLine.split(',')
if len(splitLine) == 6:
if int(splitLine[0]) > int(lastUnix):
lineToWrite = eachLine + '\n'
saveFile.write(lineToWrite)
saveFile.close()
print 'Pulled', + stock
print 'Sleeping....'
print str(datetime.datetime.fromtimestamp(time.time()).strftime('%Y-%m-%d %H:%M:%S'))
time.sleep(120)
except Exception, e:
print 'main loop', str(e)
for eachStock in stocksToPull:
pullData(eachStock)
I am hitting the operand exception bad operand type for unary +: 'str' when it gets to if int(splitLine[0]) > int(lastUnix): even though both values being compared print out as ints when tested. can anyone give me some feedback? thank you!
here is the exception response:
Currently pulling EBAY
2013-12-21 11:32:40
Pulled main loop bad operand type for unary +: 'str'
Currently pulling AAPL
2013-12-21 11:32:41
Pulled main loop bad operand type for unary +: 'str'`
You say that if int(splitLine[0]) > int(lastUnix): is causing the trouble, but you don't actually show anything which suggests that.
I think this line is the problem instead:
print 'Pulled', + stock
Do you see why this line could cause that error message? You want either
>>> stock = "AAAA"
>>> print 'Pulled', stock
Pulled AAAA
or
>>> print 'Pulled ' + stock
Pulled AAAA
not
>>> print 'Pulled', + stock
PulledTraceback (most recent call last):
File "<ipython-input-5-7c26bb268609>", line 1, in <module>
print 'Pulled', + stock
TypeError: bad operand type for unary +: 'str'
You're asking Python to apply the + symbol to a string like +23 makes a positive 23, and she's objecting.
The code works for me. (after adding missing except clause / import statements)
Did you put \ in the original code?
urlToVisit = 'http://chartapi.finance.yahoo.com/instrument/1.0/' \
+ stock + '/chartdata;type=quote;range=5d/csv'
If you omit it, it could be a cause of the exception:
>>> stock = 'GOOG'
>>> urlToVisit = 'http://chartapi.finance.yahoo.com/instrument/1.0/'
>>> + stock + '/chartdata;type=quote;range=5d/csv'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: bad operand type for unary +: 'str'
BTW, string(e) should be str(e).
I had the same error message but the cause was different. A return after tripple quotation marks was the issue.
On Python 3:
stock = "AAAA"
final_sentence="""Pulled
"""+stock+"""."""
print (final_sentence)
works, but not:
final_sentence="""Pulled"""
+stock+"""."""
print (final_sentence)
I have just started to create a distributed system that now got a single server and a bunch of clients. The language used is python and communication is done using sockets and JSON. When an error occurs on the server-side I send the error class-name and the error arguments to the client-side like this:
except Exception as e:
jsonResult = {"error":
{
"name":e.__class__.__name__,
"args": e.args
}
}
jsonResult = json.dumps(jsonResult)
jsonResult += "\n"
return jsonResult
And then try to raise it on the client-side like this:
errorFunc = decodedReply["error"]["name"]
args = decodedReply["error"]["args"]
print (args)
# Builds and appends the argumentstring to the error class-name.
errorFunc += '('
for arg in args:
# Handles when the argument is a string.
if isinstance(arg, str):
errorFunc += '\'' + arg + '\','
else:
errorFunc += arg + ','
# Removes the extra ',' from the string before adding the last ')'.
errorFunc = errorFunc[:-1]
errorFunc += ')'
# Debugging print.
print ("Here: " + errorFunc)
raise exec(errorFunc)
When I do this I get the error
TypeError: exceptions must derive from BaseException
From what I read here: Error exception must derive from BaseException even when it does (Python 2.7)
it looks like I have to declare it as a class. Is there anyway to get around that?
According to python you are raising something which is not an exception:
>>> type(exec("ValueError('ABC')"))
<class 'NoneType'>
You need to rewrite your code to have this:
>>> errorFunc = "ValueError('ABC')"
>>> exec('raise ' + errorFunc)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1, in <module>
ValueError: ABC
I'm trying to implement an assert function. How can I get the text of the failing condition into the error message? If I have to parse it from the backtrace, can I portably rely on anything about the format of frames?
AssertionError is just like any other exception in python, and assert is a simple statement that is equivalent to
if __debug__:
if not expression: raise AssertionError
or
if __debug__:
if not expression1: raise AssertionError(expression2)
so you can add a second parameter to your assertion to have additional output
from sys import exc_info
from traceback import print_exception
# assertions are simply exceptions in Python
try:
assert False, "assert was false"
except AssertionError:
print_exception(*exc_info())
outputs
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
AssertionError: assert was false
If you're sure the expression to test is secure you could do something like this:
File my_assert.py:
import sys
def my_assert(condition):
caller = sys._getframe(1)
if not eval(condition, caller.f_globals, caller.f_locals):
raise AssertionError(repr(condition) + " on line " +
str(caller.f_lineno) + ' in ' +
caller.f_code.co_name)
File test_my_assert.py:
from my_assert import my_assert
global_var = 42
def test():
local_var = 17
my_assert('local_var*2 < global_var') # OK
my_assert('local_var > global_var')
test()
Output:
Traceback (most recent call last):
File "test_my_assert.py", line 10, in <module>
test()
File "test_my_assert.py", line 8, in test
my_assert('local_var > global_var')
File "my_assert.py", line 8, in my_assert
caller.f_code.co_name)
AssertionError: 'local_var > global_var' on line 8 in test
My very hackish solution:
def my_assert(condition):
if not eval(condition):
# error stuff
Then use it by placing the condition in quotation marks. It is then a string that can be printed in the error message.
Or, if you want it to actually raise an AssertionError:
def my_assert(condition):
if not eval(condition):
raise AssertionError(condition)
I have a piece of code that acts as a listener of a button and evaluates whether some fields above this button are filled in:
def goListener(self):
if all( [self.nme.get() != "", self.dsc.get() != "", self.imp.get != ""] ):
name = self.nme.get()
desc = self.dsc.get()
while True:
try:
imp = int(self.imp.get())
break
except:
imp = int(self.imp.get())
When I run this program with different fields filled in or otherwise, it gets it right and produces the error message I ask it to with every combination except where nme and dsc are filled in but imp isn't, this produces the error message:
Traceback (most recent call last):
File "C:\Python33\lib\tkinter\__init__.py", line 1442, in __call__
return self.func(*args)
File "C:\Python33\todo.py", line 68, in goListener
imp = int(self.imp.get())
ValueError: invalid literal for int() with base 10: ''
This is running the except block by the way, which it shouldn't. Is this a problem with the evaluation, or am I missing something here?
You have:
self.imp.get != ""
You are failing to invoke the .get() method. Try:
self.imp.get() != ""
If imp = int(self.imp.get()) throws an error, calling it again outside of a try block will throw the same error.
The except block is for code that should run when there is an exception:
try:
imp = int(self.imp.get())
break
except:
print "Something bad happened"