126 continue
127 # social-media
128 try:
129 assert isinstance(data["social_media"], list)
130 except BaseException:
131 continue
121 continue
122 # chat
123 try:
124 assert isinstance(data["chat"], list)
125 except BaseException:
126 continue
127 # social-media
116 continue
117 # contributors
118 try:
119 assert isinstance(data["contributors"], str)
120 except BaseException:
121 continue
122 # chat
111 continue
112 # contact
113 try:
114 assert isinstance(data["contact"], str)
115 except BaseException:
116 continue
117 # contributors
106 continue
107 # homepage
108 try:
109 assert isinstance(data["homepage"], str)
110 except BaseException:
111 continue
112 # contact
Usage of assert
statement in application logic is discouraged. assert
is removed with compiling to optimized byte code. Consider raising an exception instead. Ideally, assert
statement should be used only in tests.
Python has an option to compile the optimized bytecode and create the respective .pyo
files by using the options -O
and -OO
. When used, these basic optimizations are done:
__debug__
built-in variable is set to False
It is recommended not to use assert
in non-test files. A better way for internal self-checks is to check explicitly and raise respective error using an if statement.
Tip: Make sure test_patterns
are defined in .deepsource.toml
to avoid false-positives. Please check the documentation to know more.
Consider this code snippet:
def read_secret(self):
assert self.is_admin, "You are unauthorized to read this"
return self._secret
If python
is run with the -O
flag, the check for self.is_admin
is
completely ignored, which can cause secrets to be leaked.
This is how you can ensure the code always works:
def read_secret(self):
if not self.is_admin:
raise AssertionError("You are unauthorized to read this")
return self._secret
Here's a more detailed example. Consider the following script foo.py
:
import sys
def run():
assert len(sys.argv) == 5 # Insecure, statement will be removed when compiled to optimized byte code
print("Argument variables are: ", sys.argv)
run()
When optimization is disabled:
$ python foo.py 1 2 3 4 5
Traceback (most recent call last):
File "foo.py", line 7, in <module>
run()
File "foo.py", line 4, in run
assert len(sys.argv) == 5 # Insecure, statement will be removed when compiled to optimized byte code
AssertionError
When optimization is enabled:
$ python -O foo.pyo 1 2 3 4 5 6
Argument variables are: ['foo.pyo', '1', '2', '3', '4', '5', '6']
Here, all the internal self-checks using the assert statements are removed, as we can see. Therefore, there's a chance for an application to behave strangely in this case. It is better do raise the Exception explicitly:
import sys
def run():
if not len(sys.argv) == 5:
raise ValueError
print("Argument variables are: ", sys.argv)
run()
Note: During autofix, DeepSource will change the assert
statements to if
statements raising AssertionError
.
This is done to replicate the existing behavior.