What Did I Do Wrong In My Function Involving Raising An Exception?
Solution 1:
There are multiple errors,so I will address the question in the title: what are the errors with raising an exception ?
To raise an exception, use raise ExceptionType(parameter)
, not return
Like this:
classInvalidCommand(Exception):
passtry:
s = raw_input("Enter a number:")
x = float(s)
except ValueError:
raise InvalidCommand(s+" is not a number")
Note that Custom exception types always need to be defined somewhere. Since InvalidCommand
is a custom Exception type (not included in Python), there should be a class definition for InvalidCommand
before using it. This class definition could go near the top of the python program file, and only needs to appear once.
For more, see Python docs -- errors and exceptions
Solution 2:
Line #37 (for loop), You are appending the value immediately from floats
, which is causing it to append the list of float twice to the output
variable.
For input mul 5 6
, it is returning ('mul', [5.0, 6.0], [5.0, 6.0])
, so the first thing you need to do it put output.append(floats)
after the loop.
for x in strdigits:
try:
float(x)
floats.append(float(x))
except ValueError:
return InvalidCommand(ValueError)
output.append(floats)
Secondly this is wrong way to do it,
x == 'add' or 'sub' or 'mul' or 'div'
Check these output from Python shell.
>>>x = 'fas'>>>x == 'add'or'sub'or'mul'or'div'
'sub'
>>>x in ['add','sub','mul','div']
False
>>>bool('sub')
True
I hope it's clear, so change your condition to
if x in ['add','sub','mul','div']:
output.append(x)
else:
raise InvalidCommand(ValueError)
to deal with invalid command
value.
As Paul suggested in comments, use raise Exception
to raise an exception.
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