Trying to make PLY work for the first time

Question

I'm new to Python and I'm having some problems trying to make PLY works. For now, all I want is to successfully run the example from the PLY homepage.

At first I tried to just download PLY-3.8, put the ply folder in the same directory I saved the example (calc.py) and ran it. The calc.py file is at the C:\Users\...\Python directory and the ply folder is the C:\Users\...\Python\ply, just to make it clearer. But I got an ImportError: No module named 'ply'.

Then I searched for a while, tried to update something called distutils and install the modules through the Windows PowerShell and so on and so forth, but none of that worked and I just reset the whole thing (reinstalling Python and all of that). But then I finally got it to work by simply inserting into the sys.path the directory path where the script I was running (edit: in interactive mode) was, by doing this:

import sys
sys.path.insert(0,'C:\\Users\\ ... \\Python')

This fixed the ImportError but, and this is where I am now, there are a bunch of other errors:

Traceback (most recent call last):
  File "C:\Users\...\Python\calc.py", line 48, in <module>
    lexer = lex.lex()
  File "C:\Users\...\Python\ply\lex.py", line 906, in lex
    if linfo.validate_all():
  File "C:\Users\...\Python\ply\lex.py", line 580, in validate_all
    self.validate_rules()
  File "C:\Users\...\Python\ply\lex.py", line 822, in validate_rules
    self.validate_module(module)
  File "C:\Users\...\Python\ply\lex.py", line 833, in validate_module
    lines, linen = inspect.getsourcelines(module)
  File "c:\users\...\python\python35\lib\inspect.py", line 930, in getsourcelines
    lines, lnum = findsource(object)
  File "c:\users\...\python\python35\lib\inspect.py", line 743, in findsource
    file = getsourcefile(object)
  File "c:\users\...\python\python35\lib\inspect.py", line 659, in getsourcefile
    filename = getfile(object)
  File "c:\users\...\python\python35\lib\inspect.py", line 606, in getfile
    raise TypeError('{!r} is a built-in module'.format(object))
TypeError: <module '__main__'> is a built-in module

Now I have absolutely no idea what to do. I tried to search for a solution but had no luck. I appreciate if anyone can help me out.

I'm on Windows 10, using Python 3.5.0 and iep as my IDE (www.iep-project.org) if these informations are of any importance.

In short: I just want to successfully run the example from the PLY homepage and then I think I can figure out the rest.

EDIT: I found out that if I do:

import inspect
inspect.getfile(__main__)

I get the exact same (last) error from before:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "c:\users\...\python\python35\lib\inspect.py", line 606, in getfile
    raise TypeError('{!r} is a built-in module'.format(object))
TypeError: <module '__main__'> is a built-in module

I think this is the culprit, but I still don't know how to fix it.

EDIT 2: I got it to work and answered the question explaining how, but if someone have a more complete answer, I would love to hear it.

Answer 1

To anyone having this problem, I found what was the issue. I still don't know why exactly is like that, so if anyone have a more complete answer to provide I would appreciate (I'm still a newbie at Python).

Anyway, it seems this code can't be executed in Interactive mode, it needs to be executed as a script. To do that on IEP it's Run > Run file as script or Ctrl+Shift+E. On IDLE you need to Open... the file (Ctrl+O) and then Run Module (F5).

As to why it can't be executed in Interactive mode, here's a little bit about the difference between interactive mode and running as script from the IEP wizard:

Interactive mode vs running as script

You can run the current file or the main file normally, or as a script. When run as script, the shell is restared (sic) to provide a clean environment. The shell is also initialized differently so that it closely resembles a normal script execution.

In interactive mode, sys.path[0] is an empty string (i.e. the current dir), and sys.argv is set to [''].

In script mode, __file__ and sys.argv[0] are set to the scripts filename, sys.path[0] and the working dir are set to the directory containing the script.

That explains a bit about why the inspect.getfile(__main__) was throwing an error: the __main__ had no attribute __file__. And also why I had to insert the current directory into sys.path: sys.path didn't had the current directory in interactive mode.

I hope this helps someone.