In the past I've mainly use PyLint - it can highlight when you used an undefined variable, when you import things without using them and so on.
It can be a bit verbose, complaining about things like lines being over 80 character long, variable not matching to specific regex's, classes having too few public methods, methods missing docs-trings.
For example, for script..
import os
import somefakelib
def myfunc(x):
blah = "Something"
print os.listdir( x+blh )
PyLint generates the following messages:
C: 1: Missing docstring
F: 2: Unable to import 'somefakelib' (No module named somefakelib)
C: 4:myfunc: Missing docstring
C: 4:myfunc: Invalid name "x" (should match [a-z_][a-z0-9_]{2,30}$)
C: 4:myfunc: Invalid name "x" (should match [a-z_][a-z0-9_]{2,30}$)
E: 6:myfunc: Undefined variable 'blh'
W: 5:myfunc: Unused variable 'blah'
W: 2: Unused import somefakelib
They are all valid complaints, but I tend to disable a lot of the convention and refactoring messages. You can disable specific messages, either as comments in your code:
#pylint:disable-msg=R0903,C0103,R0903,F0401,C0301
..or as command line arguments to the PyLint command:
pylint --disable-msg=R0903,C0103,R0903,F0401,C0301 myfile.py
With the above messages disabled, it generates the following messages for the above code:
C: 1: Missing docstring
C: 4:myfunc: Missing docstring
E: 6:myfunc: Undefined variable 'blh'
W: 5:myfunc: Unused variable 'blah'
W: 2: Unused import somefakelib
PyLint also generates a "code report", including how many lines of code/comments/docstring/whitespace the file has, number of messages per-category, and gives your code a "score" - 10 being no messages, 0 generally being a syntax error
Another option is PyFlakes, which I find a little less excessively-verbose (I've recently started using it in place of PyLint). Again using the above script, PyFlakes gives the following messages:
example.py:2: 'somefakelib' imported but unused
example.py:6: undefined name 'blh'
The final option I use is pep8.py, which as the name suggests enforces PEP8. It is by far the most.. pedantic script, enforcing things like correct blank-lines before/after functions/classes, spacing around code, correct 4-space indentation and so on..
Running on the code above, it produces the following:
example.py:4:1: E302 expected 2 blank lines, found 1
example.py:6:23: E201 whitespace after '('
example.py:6:32: W292 no newline at end of file
It is mostly enforces stylistic things like correct whitespace, it does not do much static-analysis of the code like PyLint or PyFlakes, so I use pep8.py in conjunction with either PyLint or PyFlakes.
pep8.py was originally announced on the python mailing list here, but the download link in this is now dead.. There's a github mirror by cburroughs, with a few minor fixes at github.com/cburroughs/pep8.py, or you can grab the unmodified version from an older revision
PyChecker is another option, although I haven't use it
