__del__ is called explicitly¶
ID: py/explicit-call-to-delete
Kind: problem
Security severity:
Severity: warning
Precision: very-high
Tags:
- reliability
- correctness
Query suites:
- python-security-and-quality.qls
Click to see the query in the CodeQL repository
The __del__ special method is designed to be called by the Python virtual machine when an object is no longer reachable, but before it is destroyed. Calling a __del__ method explicitly may cause an object to enter an unsafe state.
Recommendation¶
If explicit clean up of an object is required, a close() method should be called or, better still, wrap the use of the object in a with statement.
Example¶
In the first example, rather than close the zip file in a conventional manner the programmer has called __del__. A safer alternative is shown in the second example.
def extract_bad(zippath, dest):
zipped = ZipFile(zippath)
try:
zipped.extractall(dest)
finally:
zipped.__del__()
def extract_good(zippath, dest):
zipped = ZipFile(zippath)
try:
zipped.extractall(dest)
finally:
zipped.close()
References¶
Python Standard Library: object.del