org.sonar.l10n.py.rules.python.S5828.html Maven / Gradle / Ivy
This rule raises an issue when an invalid "mode" is provided to the open builtin function.
Why is this an issue?
The open builtin function can open files in different modes. These modes are provided as a combination of characters. Using an invalid
sequence of characters will make open fail with a ValueError.
A valid mode:
- should contain only one of the following characters:
r (read), w (write), a (append), x
(create).
- should contain zero or one of the following characters:
t (text), b (binary).
- should contain zero or one
+ character (open for updating)
For example: a, rt, r+ and w+b are valid modes.
If no t or b character is provided the mode will default to t (text), so specifying r is
equivalent to rt.
Note: In Python 2, providing an incorrect mode may have an undefined behavior (ex: it might ignore some characters)
How to fix it
Make sure to provide a valid mode to the open builtin function.
Code examples
Noncompliant code example
In Python 3 the following program will throw a ValueError.
In Python 2.7.16 on MacOs, open will just ignore the w flag.
with open("test.txt", "aw") as f: # Noncompliant: ValueError
pass
Compliant solution
with open("test.txt", "a") as f:
pass
Pitfalls
In Python 2, the character U (universal newlines) is available as a mode character but it cannot be combined with a,
w, x or +.
Note: U has no effect in Python 3, it is deprecated and is replaced by the parameter newline of the
open function. The default value of newline is None, meaning universal newlines mode is enabled.
Resources
Documentation