# If there is no __init__.py next to the file its not in a package

# so can't be a relative import.

if not exists(join(dirname(base_path), '__init__.py')):

return False

try:

for count, r in self._recursive_matches(nodes, 0):

if self.name:

r[self.name] = nodes[:count]

yield count, r

except RuntimeError:

# We fall back to the iterative pattern matching scheme if the recursive

# scheme hits the recursion limit.

for count, r in self._iterative_matches(nodes):

if self.name:

r[self.name] = nodes[:count]

yield count, r

def _iterative_matches(self, nodes):

"""Helper to iteratively yield the matches."""

nodelen = len(nodes)

if 0 >= self.min:

yield 0, {}

results = []

# generate matches that use just one alt from self.content

for alt in self.content:

for c, r in generate_matches(alt, nodes):

yield c, r

results.append((c, r))

# for each match, iterate down the nodes

while results:

new_results = []

for c0, r0 in results:

# stop if the entire set of nodes has been matched

if c0 < nodelen and c0 <= self.max:

for alt in self.content:

for c1, r1 in generate_matches(alt, nodes[c0:]):

if c1 > 0:

r = {}

r.update(r0)

r.update(r1)

yield c0 + c1, r

new_results.append((c0 + c1, r))

results = new_results

Files in this directory:

- py2_test_grammar.py -- test file that exercises most/all of Python 2.x's grammar.

- py3_test_grammar.py -- test file that exercises most/all of Python 3.x's grammar.

- infinite_recursion.py -- test file that causes lib2to3's faster recursive pattern matching

scheme to fail, but passes when lib2to3 falls back to iterative pattern matching.