Unguarded next inside generator PTC-W0063
Bug risk
Critical
2 months ago
—
3 years old
Call to
next() should be wrapped in try-except1621
1622 # Try reading header
1623 reader = csv.reader(fileobj, store.dialect)
1624 header = next(reader)1625 fileobj.close()
1626
1627 # Check if the file is not two column onlyCall to
next() should be wrapped in try-except 93 # value can be None or blank stringfor cells having formatting only,
94 # we need to ignore such columns as that would be treated like "" fields
95 # later in the translate-toolkit
96 fields = [cell.value for cell in next(worksheet.rows) if cell.value] 97 for row in worksheet.rows:
98 values = [cell.value for cell in row]
99 values = values[: len(fields)]Call to
next() should be wrapped in try-except204 raise MemoryImportError(
205 gettext("Could not parse TMX file: %s") % error
206 ) from error
207 header = next(208 storage.document.getroot().iterchildren(storage.namespaced("header"))
209 )
210 lang_cache = {}
Description
Calls to next() should be inside try-except block.
When the iterator is exhausted, StopIteration exception is raised. When used inside a generator, this can cause unexpected behavior. If not handled, it will propagate out of the generator causing termination. PEP-479 has been accepted to fix this problem. It will modify the behavior of StopIteration in generators.
Each call to next() should be wrapped in a try-except block to explicitly handle StopIteration exceptions.
Bad practice
def get_team_structure(team):
for team in class:
students = iter(team)
# StopIteration exception will be raised if team doesn't have members.
leader = next(students)
members = [m for m in students]
yield leader, members
def print_teams(teams):
for leader, members in get_team_structure(teams):
print("Leader: "leader)
for member in members:
print(member)
Recommended:
def get_team_structure(team):
for team in class:
# StopIteration exception will be raised if team has no members.
students = iter(team)
# Added `try` block, to guard against the exception
try:
leader = next(students)
except StopIteration:
# team has no members, skip it
continue
members = [m for m in students]
yield leader, members
def print_teams(teams):
for leader, members in get_team_structure(teams):
print("Leader: "leader)
for member in members:
print(member)
...