Can python doctest ignore some output lines?

Question

I'd like to write a doctest like this:

""" >>> print a.string()           foo : a           bar : b          date : <I don't care about the date output>           baz : c """ 

Is there any way to do this? I think it would make more sense to switch to unittest, but I'm curious whether it's possible to specify a range of output that shouldn't be matched for the test in doctest.

Thanks!

Answer 1

With doctest.ELLIPSIS, you can use ... to mean "match any string here". You can set doctest options with a doctest directive, to make it active for just one test case: one example in the online docs is:

>>> print range(20) # doctest:+ELLIPSIS [0, 1, ..., 18, 19] 

If you want a doctest option to be active throughout, you can pass it as the optionflags= argument to whatever doctest functions you use, e.g. doctest.testfile. (You can pass multiple option flags there by using the | operator to bit-or them).

Answer 2

Responding to questions about "how can we ignore the whole line": yes, the fact that "..." also looks like a continuation like makes it hard to ignore the entire output. You can use "#doctest: +SKIP" if you just want to skip the example entirely, but that won't work if you are relying on its side-effects. If you really need to do this, I suppose you could monkey-patch the doctest module itself, though I wouldn't particularly recommend it:

>>> import doctest >>> doctest.ELLIPSIS_MARKER = '-etc-' >>> print 12 # doctest: +ELLIPSIS -etc- 

(this test passes.)

Or you could temporarily suppress stdout and/or stderr:

>>> # Suppress stdout >>> import sys >>> class DevNull: ...     def noop(*args, **kwargs): pass ...     close = write = flush = writelines = noop >>> sys.stdout = DevNull() >>> # Run a test and ignore output (but we need its side effects) >>> print 12 # NOTE: stdout is suppressed! >>> # Restore stdout >>> sys.stdout = sys.__stdout__ 

(this test also passes.)