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Executing the following code against a py file which contains line continuations generates an assert:
import tokenize
foofile = open(filename, "r")
tokenize.untokenize(list(tokenize.generate_tokens(foofile.readline)))
(note, the list() is important due to issue #8478)
The assert triggered is:
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "C:\Python27\lib\tokenize.py", line 262, in untokenize
 return ut.untokenize(iterable)
 File "C:\Python27\lib\tokenize.py", line 198, in untokenize
 self.add_whitespace(start)
 File "C:\Python27\lib\tokenize.py", line 187, in add_whitespace
 assert row <= self.prev_row
AssertionError
I have tested this in 2.6.5, 2.7 and 3.1.2. The line numbers may differ but the stack is otherwise identical between these versions.
Example input code:
foo = \
 3
If the assert is removed, the code generated is still incorrect. For example, the input:
foo = 3
if foo == 5 or \
 foo == 1
 pass
becomes:
foo = 3
if foo == 5 orfoo == 1
 pass
which besides not having the line continuation, is functionally incorrect.
I'm wrapping my head around the functionality of this module and am willing to do the legwork to get a fix in. Ideas on how to go about it are more than welcome.
Ironic aside: this bug is present when tokenize.py itself is used as input.