Having read this question I can understand why this warning might be output, but I have a specific case when the loop variable can not be undefined...
for i in range(0, 2):
print i
print i
PyLinting the above I get
W: 4,6: Using possibly undefined loop variable 'i'
Is PyLint not clever enough to note that the built in range() function will always produce a populated list in this case and so i will always be set for the last print statement? I can understand if it was a under-defined function, because PyLint could not possibly know what the function does... but in this case it is a well known function and surely this usage would be common?
If so, is it better to supress the warning or define i before the loop (which seems wasteful)?
This is because your range might be empty depending on the intermediate execution steps involved, or it may be have redefined within the code as pointed by @tobias_k (though that will throw an additional W: 1, 0: Redefining built-in 'range' (redefined-builtin)), and hence, variable i may not be defined.
Note that pylint doesn't at all execute code, it just does static analysis, so it won't check the value within the range. So when it sees a variable defined within a for block being re-used possibly out of scope, it complains.
Consider the examples below, where the same Warning is shown by pylint but one runs, while other throws an exception:
W: 4, 6: Using possibly undefined loop variable 'i' (undefined-loop-variable)
Example (Not Working):
$ cat test.py
for i in range(0):
print i
print i
$ python test.py
Traceback (most recent call last):
File "test.py", line 4, in <module>
print i
NameError: name 'i' is not defined
Example (Working):
$ cat test.py
for i in range(0, 2):
print i
print i
$ python test.py
0
1
1
As the answer to your question, is it better to suppress the warning, my answer would be no. If you do want to suppress it, make sure you re-enable it after the code block in question.