assert 0, "foo" vs. assert(0, "foo")

[Thomas Guettler]

Hi,

Python 2.3.3 (#1, Feb 5 2005, 16:22:10) [GCC 3.3.3 (SuSE Linux)] on linux2

assert 0, "foo" Traceback (most recent call last):
File "<stdin>", line 1, in ?
AssertionError: foo assert(0, "foo")

If you use parenthesis for the assert statement, it never
raises an exception.

Up to now I raised strings, but since this is deprecated,
I switched to use the second argument for the assert
statement.

Is it possible to change future python versions, that
assert accept parenthesis?

Thomas

--
Thomas Güttler, http://www.thomas-guettler.de/

[Daniel Fackrell]

> "Thomas Guettler" <gu*****@thomas-guettler.de> wrote in message

news:pa****************************@thomas-guettler.de...
Hi, Python 2.3.3 (#1, Feb 5 2005, 16:22:10) [GCC 3.3.3 (SuSE Linux)] on linux2

assert 0, "foo"
Assert that 0 is true. If that fails, raise AssertionError("foo").
Traceback (most recent call last):
File "<stdin>", line 1, in ?
AssertionError: foo

assert(0, "foo")

Assert that the tuple (0, "foo") is true. Non-empty tuples are always true.

If you use parenthesis for the assert statement, it never
raises an exception.

Up to now I raised strings, but since this is deprecated,
I switched to use the second argument for the assert
statement. Is it possible to change future python versions, that
assert accept parenthesis?
As shown above, it does, but it doesn't do quite what you expected. For
further enlightenment, try the following and think through why each one
gives the results it does:

assert (), 'spam'
assert [], 'eggs'
assert {}, 'spam and eggs'
assert (0,), 'spam, spam, and eggs'
assert (0, "foo"), 'spam, spam, eggs, and spam'
assert 0, "foo", 'shrubbery'

The last will give a syntax error. Can you spot why?
Thomas --
Thomas Güttler, http://www.thomas-guettler.de/

[Scott David Daniels]

Thomas Guettler wrote:

Hi,

Python 2.3.3 (#1, Feb 5 2005, 16:22:10) [GCC 3.3.3 (SuSE Linux)] on linux2

assert 0, "foo"
Traceback (most recent call last):
File "<stdin>", line 1, in ?
AssertionError: foo
assert(0, "foo")

If you use parenthesis for the assert statement, it never
raises an exception.

Up to now I raised strings, but since this is deprecated,
I switched to use the second argument for the assert
statement.

Is it possible to change future python versions, that
assert accept parenthesis?

You are confusing assert with raise.

assert test, text

behaves like:

if __debug__ and test:
raise AssertionError, text

As far as raise goes, where you have been writing:

raise "some complaint"

you could simply use:

raise ValueError, "some complaint"

or:

raise ValueError("some complaint")

--Scott David Daniels
Sc***********@Acm.Org

[Carl Banks]

Thomas Guettler wrote:

Is it possible to change future python versions, that
assert accept parenthesis?

It's possible, but extremely unlikely that it will ever happen. assert
is not a function, but a statement (like print). Statements don't use
parentheses; when you use parentheses, it considers that a tuple.

For example, if you try this with print:

print ("hello","world")

you see that in prints out a tuple value, rather than treating "hello"
and "world" as arguments. Same thing with assert.
--
CARL BANKS