Unnecessary ‘else’ clause in loop¶
ID: py/redundant-else
Kind: problem
Security severity:
Severity: warning
Precision: very-high
Tags:
- quality
- maintainability
- useless-code
Query suites:
- python-security-and-quality.qls
Click to see the query in the CodeQL repository
The else clause of a loop (either a for or a while statement) executes immediately after the loop terminates normally. If there is a break statement in the loop body, then the else clause is skipped. If there is no break statement, then the else clause will always be executed after the loop, unless it exits with a return or raise. Therefore, if there is no break statement in the loop body then the else clause can be replaced with unindented code.
Generally the use of else clauses should be avoided where possible, as they are likely to be misunderstood.
Recommendation¶
Replace the else clause with unindented code.
Example¶
In this example, the pointless_else function contains a redundant else clause. The else clause can be simplified, as shown in the no_else function, which has the same semantics, but has no else clause. The third example function, with_break, shows a version where the else clause is necessary, as the break statement skips the else clause.
def pointless_else(container):
for item in container:
if of_interest(item):
return item
else:
raise NotFoundException()
def no_else(container):
for item in container:
if of_interest(item):
return item
raise NotFoundException()
def with_break(container):
for item in container:
if of_interest(item):
found = item
break
else:
raise NotFoundException()
return found
References¶
Python Language Reference: The while statement.
Python Tutorial: Break and continue statements, and else clauses on loops.