Question

I want to create a kind of utility class which contains only static methods which are callable by the name class prefix. Looks like I’m doing something wrong 🙂

Here is my small class:

class FileUtility():

    @staticmethod
    def GetFileSize(self, fullName):
        fileSize = os.path.getsize(fullName)
        return fileSize

    @staticmethod
    def GetFilePath(self, fullName):
        filePath = os.path.abspath(fullName)
        return filePath

Now my “main” method:

from FileUtility import *
def main():
        path = 'C:\config_file_list.txt'
        dir = FileUtility.GetFilePath(path)
        print dir

and I got an error: unbound method GetFilePath() must be called with FileUtility instance as first argument (got str instance instead).

A have a few questions here:

1. What am I doing wrong? Should not the static method be callable by classname?
2. Do I really need a utility class, or are there other ways to achieve the same in Python?
3. If I try to change the code in main I’m getting: TypeError: GetFilePath() takes exactly 1 argument (2 given)

The new main:

from FileUtility import *
def main():
    objFile = FileUtility()
    path = 'H:\config_file_list.txt'
    dir = objFile.GetFilePath(path)
    print dir

Answer 1

You’re getting the error because you’re taking a self argument in each of those functions. They’re static, you don’t need it.

However, the ‘pythonic’ way of doing this is not to have a class full of static methods, but to just make them free functions in a module.

#fileutility.py:

def get_file_size(fullName):
    fileSize = os.path.getsize(fullName)
    return fileSize


def get_file_path(fullName):
    filePath = os.path.abspath(fullName)
    return filePath

Now, in your other python files (assuming fileutility.py is in the same directory or on the PYTHONPATH)

import fileutility

fileutility.get_file_size("myfile.txt")
fileutility.get_file_path("that.txt")

It doesn’t mention static methods specifically, but if you’re coming from a different language, PEP 8, the python style guide is a good read and introduction to how python programmers think.