How to count lines of code in Python excluding comments and docstrings?

Tahar doesn't count the docstrings. Here's its count_loc function :

def count_loc(lines):
    nb_lines  = 0
    docstring = False
    for line in lines:
        line = line.strip()

        if line == "" \
           or line.startswith("#") \
           or docstring and not (line.startswith('"""') or line.startswith("'''"))\
           or (line.startswith("'''") and line.endswith("'''") and len(line) >3)  \
           or (line.startswith('"""') and line.endswith('"""') and len(line) >3) :
            continue

        # this is either a starting or ending docstring
        elif line.startswith('"""') or line.startswith("'''"):
            docstring = not docstring
            continue

        else:
            nb_lines += 1

    return nb_lines

Comment lines can be lines of code in python. See doctest for example.

Moreover, you will have trouble to find a sensible/reliable way to consider a case like this as being a comment or code:

foo = ('spam', 
       '''eggs
          eggs
          eggs'''
       '''more spam''',
       'spam')

Just count the comment lines as well, I think most programmers will agree it is as good a measure for whatever you are actually trying to measure.

It is probably correct to include Python docstrings in a "lines of code" count. Normally a comment would be discarded by the compiler, but docstrings are parsed:

See PEP 257 - Docstring Conventions:

A docstring is a string literal that occurs as the first statement in a module, function, class, or method definition. Such a docstring becomes the __doc__ special attribute of that object.

...

String literals occurring elsewhere in Python code may also act as documentation. They are not recognized by the Python bytecode compiler and are not accessible as runtime object attributes..

In other words, docstrings are compiled and constitute, in a very real way, the code of the program. Additionally, they're commonly used by the doctest module for unit testing, as usage strings for command line utilities, and so on.

Have you looked at http://www.ohloh.net/p/ohcount - always been pretty on the money for me - although I do not use python