I'm writing per the following, in which I try to produce a decent error message when comparing two multiline blocks of Unicode text. The interior method that does the comparison raises an assertion, but the default explanation is useless to me
I need to add something to code such as this below:
def assert_long_strings_equal(one, other):
lines_one = one.splitlines()
lines_other = other.splitlines()
for line1, line2 in zip(lines_one, lines_other):
try:
my_assert_equal(line1, line2)
except AssertionError, error:
# Add some information to the printed result of error??!
raise
I cannot figure out how to change the printed error message in the assertionerror I catch. I always get AssertionError: u'something' != 'something else'
, which only shows the first line of the output.
How can I change the assertion message to print out whatever I want?
If it's relevant, I am using nose
to run the test.
assert expression, info
For instance,
>>> assert False, "Oopsie"
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AssertionError: Oopsie
From the docs:
Assert statements are a convenient way to insert debugging assertions into a program:
assert_stmt ::= "assert" expression ["," expression]
The simple form,
assert expression
, is equivalent toif __debug__: if not expression: raise AssertionError
The extended form
assert expression1, expression2
is equivalent to
if __debug__: if not expression1: raise AssertionError(expression2)
These equivalences assume that
__debug__
andAssertionError
refer to the built-in variables with those names. In the current implementation, the built-in variable__debug__
is True under normal circumstances, False when optimization is requested (command line option -O). The current code generator emits no code for an assert statement when optimization is requested at compile time. Note that it is unnecessary to include the source code for the expression that failed in the error message; it will be displayed as part of the stack trace.