Python Puzzle

Let me start with the confession that I am not an expert Python developer so this might not be a surprise for some of you. Yesterday, I was working on a Python REST API client using awesome requests library for one of my server application. To quickly hack my client, I created a Python virtual environment using virtualenv and installed required libraries using pip. I was ready to play with Python(again). I created a new file and added a method. For demonstration, let’s suppose our method is called hello, as shown below.

def hello(name):
    return "Hello, {0}".format(name)

I fired up Python REPL and imported

→ python
Python 2.7.10 (default, Jul 14 2015, 19:46:27)
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import abc

All is looking great. I can call hello method now. I fired the command and was greeted with following error message.

>>> abc.hello("shekhar")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'hello'

To me it was something very basic and should have worked. I looked up all methods of abc using dir method. There is no hello method.

>>> dir(abc)
['ABCMeta', 'WeakSet', '_C', '_InstanceType', '__builtins__', '__doc__', '__file__', '__name__', '__package__', 'abstractmethod', 'abstractproperty', 'types']

What’s possible is wrong? I couldn’t figure out what’s wrong with my After spending some time on it, I just decided to copy and paste example from Python documentation for modules. They have an example where a file contains a method fib. When I followed their example, it worked fine. I was able to call fib method fibo.fib.

So, I decided to rename to Voila! I can call my hello method.

>>> import hello
>>> hello.hello("Shekhar")
'Hello, Shekhar'

But, what’s the issue with name

I googled python and found out that there in the core Python library My first reactive was who creates a module named in the core library. From the documentation,

This module provides the infrastructure for defining abstract base classes (ABCs) in Python, as outlined in PEP 3119; see the PEP for why this was added to Python.

When we imported our Python basically imported abc module of Python core. So, it never imported our code. This is the reason hello method was not available on abc.

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