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I have a fair background in java, trying to learn python. I'm running into a problem understanding how to access methods from other classes when they're in different files. I keep getting module object is not callable.

I made a simple function to find the largest and smallest integer in a list in one file, and want to access those functions in another class in another file.

Any help is appreciated, thanks.

class findTheRange():

    def findLargest(self, _list):
        candidate = _list[0]
        for i in _list:
            if i > candidate:
                candidate = i
        return candidate

    def findSmallest(self, _list):
        candidate = _list[0]
        for i in _list:
            if i < candidate:
                candidate = i
        return candidate

 import random
 import findTheRange

 class Driver():
      numberOne = random.randint(0, 100)
      numberTwo = random.randint(0,100)
      numberThree = random.randint(0,100)
      numberFour = random.randint(0,100)
      numberFive = random.randint(0,100)
      randomList = [numberOne, numberTwo, numberThree, numberFour, numberFive]
      operator = findTheRange()
      largestInList = findTheRange.findLargest(operator, randomList)
      smallestInList = findTheRange.findSmallest(operator, randomList)
      print(largestInList, 'is the largest number in the list', smallestInList, 'is the                smallest number in the list' )
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4
  • 9
    Python is not Java. None of this code has any reason to be in a class. Make them module-level functions. Commented May 27, 2013 at 21:04
  • 2
    In a more complicated python program, wouldn't i need all my methods organized in classes, I'm still thinking java, thanks for the help. Commented May 27, 2013 at 21:18
  • 5
    No, you will need some classes, but you will probably need plain functions too. Commented May 27, 2013 at 21:22
  • Happens a lot... A weird error when trying to implement Object Oriented Programming techniques Commented Feb 14, 2019 at 7:08

2 Answers 2

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82

The problem is in the import line. You are importing a module, not a class. Assuming your file is named other_file.py (unlike java, again, there is no such rule as "one class, one file"):

from other_file import findTheRange

if your file is named findTheRange too, following java's convenions, then you should write

from findTheRange import findTheRange

you can also import it just like you did with random:

import findTheRange
operator = findTheRange.findTheRange()

Some other comments:

a) @Daniel Roseman is right. You do not need classes here at all. Python encourages procedural programming (when it fits, of course)

b) You can build the list directly:

  randomList = [random.randint(0, 100) for i in range(5)]

c) You can call methods in the same way you do in java:

largestInList = operator.findLargest(randomList)
smallestInList = operator.findSmallest(randomList)

d) You can use built in function, and the huge python library:

largestInList = max(randomList)
smallestInList = min(randomList)

e) If you still want to use a class, and you don't need self, you can use @staticmethod:

class findTheRange():
    @staticmethod
    def findLargest(_list):
        #stuff...
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5 Comments

Those two lines are identical to OP's code. The changed import fixes the error, but using OP's filename (and explaining the apparent redundancy) might help.
they are not identical - it is a dynamic call instead of a static one. (please correct me if I am wrong)
and I don't know what the OP's filename is - I only guess it really is findTheRange, since that's the convention in Java. anyway, you are welcome to improve my answer.
You're right that the lines aren't identical, mea culpa. However, the guess that the module name is findTheRange is a very safe one (it's imported, it's used as if it was the class, as you note it's the Java convention).
It should be stated that imports are relative to the current file. I also would add clarification that from <directory> import <file> often becomes from <pseudo_dir> import <file> if dealing with a structure that mixes Packages and Folders. PyCharm nicely denotes this in its "Project Explorer".
3
  • from a directory_of_modules, you can import a specific_module.py
  • this specific_module.py, can contain a Class with some_methods() or just functions()
  • from a specific_module.py, you can instantiate a Class or call functions()
  • from this Class, you can execute some_method()

Example:

#!/usr/bin/python3
from directory_of_modules import specific_module
instance = specific_module.DbConnect("username","password")
instance.login()

Excerpts from PEP 8 - Style Guide for Python Code:

Modules should have short and all-lowercase names.

Notice: Underscores can be used in the module name if it improves readability.

A Python module is simply a source file(*.py), which can expose:

  • Class: names using the "CapWords" convention.

  • Function: names in lowercase, words separated by underscores.

  • Global Variables: the conventions are about the same as those for Functions.

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1 Comment

Can't you import the class from the specific module?

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