Spelling mistakes!

[KraftDiner]

I've spent hours trying to find a bug that was a simple spelling
mistake.

in an init method I declare a variable self.someLongNa me

later in a different method of the class I use
self.sumLongNam e
Now I really meant self.someLongNa me.
In fact I don't want a variable called sumLongName.
Frankly how are you ever to know if this type of error is occuring?

[Heiko Wundram]

KraftDiner wrote:

Frankly how are you ever to know if this type of error is occuring?

By the traceback:

modelnine@phoen ix ~ $ python
Python 2.4.2 (#1, Dec 22 2005, 17:27:39)
[GCC 4.0.2 (Gentoo 4.0.2-r2, pie-8.7.8)] on linux2
Type "help", "copyright" , "credits" or "license" for more information.

class x(object): .... def __init__(self):
.... self.somename = "hello"
.... def somemethod(self ):
.... print self.sumname
.... a = x()
a.somemethod() Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "<stdin>", line 5, in somemethod
AttributeError: 'x' object has no attribute 'sumname'

AttributeError describes just this. And please don't start the war on how
much better compiled languages are because they catch this kind of error at
compile time. They simply are not.

--- Heiko.

[Fuzzyman]

VBScript allows you to specify that variable names be declared. I used
to think this was good - until I realised that Python allows you to
dynamically assign attributes in namespaces using all sorts of tricks.

(Setattr, using __dict__ etc).

It's just not possible with Python. Rarely happens to me in practise
and is easy to fix.

All the best,

Fuzzyman
http://www.voidspace.org.uk/python/index.shtml

[KraftDiner]

try this:

class x(object):
def __init__(self):
self.someName = "hello"
def someMethod(self ):
self.sumName = "bye"

find that bug.

[Xavier Morel]

KraftDiner wrote:

I've spent hours trying to find a bug that was a simple spelling
mistake.

in an init method I declare a variable self.someLongNa me

later in a different method of the class I use
self.sumLongNam e
Now I really meant self.someLongNa me.
In fact I don't want a variable called sumLongName.
Frankly how are you ever to know if this type of error is occuring?

PyChecker and PyLint sound like the perfect remedy to this issue (I know
one of them is able to warn you if you *create* an attribute outside of
__init__, maybe both are but at least one of them is)

I just run them when I save my files, they don't take long and even
though the default configuration is *extremely* annoying (especially
PyLint's, it generates heaps of warnings) once configured to one's need,
they're extremely valuable for both personal and team development.

[André]

KraftDiner wrote:

try this:

class x(object):
def __init__(self):
self.someName = "hello"
def someMethod(self ):
self.sumName = "bye"

find that bug.

Write a test for each method before writing the method.

Write the code once; read it critically (at least) twice.

If you find that too difficult, use a different programming language
(one in which you have to declare every variable) and become less
productive.

A.

[Peter Hansen]

KraftDiner wrote:

try this:

class x(object):
def __init__(self):
self.someName = "hello"
def someMethod(self ):
self.sumName = "bye"

find that bug.

You forgot to include unit tests for someMethod(). Those would have
caught the bug.

The reality is that if you aren't doing unit testing, you aren't
catching other bugs either, bugs which aren't caught by the compile-time
tests in other languages and which aren't caught by PyChecker or PyLint
either. Bugs which are probably much more common than typos like the
above, too.

Still, if you are really bothered by these things frequently, I believe
recipes have been posted in the past which *do* allow you to avoid many
such problems, by declaring the acceptable attribute names somewhere and
using one of Python's many hooks to intercept and check attribute
setting. Check the archives or the CookBook.

-Peter

[skip]

try this:
class x(object):
def __init__(self):
self.someName = "hello"
def someMethod(self ):
self.sumName = "bye" find that bug.

Aside from the other responses (unittests, pychecker/pylint), you might also
consider using __slots__ for new-style classes:

class x(object):
__slots__ = ('someName',)
def __init__(self):
self.someName = "hello"
def someMethod(self ):
self.sumName = "bye"

my_x = x()
my_x.someMethod ()

When run you will get this output:

Traceback (most recent call last):
File "slot.py", line 9, in <module>
my_x.someMethod ()
File "slot.py", line 6, in someMethod
self.sumName = "bye"
AttributeError: 'x' object has no attribute 'sumName'

Skip

[Terry Hancock]

On 6 Jan 2006 07:30:41 -0800
"KraftDiner " <bo*******@yaho o.com> wrote:

I've spent hours trying to find a bug that was a simple
spelling mistake.
You're not the first. ;-)
in an init method I declare a variable self.someLongNa me

later in a different method of the class I use
self.sumLongNam e
Now I really meant self.someLongNa me.
In fact I don't want a variable called sumLongName.
Frankly how are you ever to know if this type of error is
occuring?

Both "unit tests" and "interfaces " are useful for catching
simple errors like this one. There is a 'unittest' module
in the Python standard library, and 'interface' modules are
available from the Zope 3 project and PyProtocols, both are
good.

Once you know you have a problem like this (or you've
decided to change a spelling), you can track down the
problem using grep, fix it with sed or use Python itself to
do the job if you really want to.

I once misspelled a name in a set of API methods, which was
very embarrassing (I spelled "fovea" as "fovia"). So then I
had to go through and change it, and report it in as an API
change so that a "patch" became a "minor version upgrade".
Duh. Next time I use a dictionary before freezing an API!

Cheers,
Terry

--
Terry Hancock (ha*****@Anansi Spaceworks.com)
Anansi Spaceworks http://www.AnansiSpaceworks.com

[Steven D'Aprano]

On Fri, 06 Jan 2006 17:23:27 -0600, Terry Hancock wrote:

I once misspelled a name in a set of API methods, which was
very embarrassing (I spelled "fovea" as "fovia"). So then I
had to go through and change it, and report it in as an API
change so that a "patch" became a "minor version upgrade".
Duh. Next time I use a dictionary before freezing an API!

Can you please explain what you mean by that? Use a dictionary how?

--
Steven.