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python_install

Python

Installation and Requirements

Mystic BBS has an embedded Python scripting engine called Mystic Python. This engine is based on Python 2.7 and is compatible with all Python 2.7 code and modules. In order for this to function properly, Mystic requires that Python 2.7 is installed on the operating system. Python is not a dependency for Mystic to function, so if you do not plan to execute Python scripts then you do not need to have Python installed if you do not wish to use it.

Note: The “bit level” of Python must match the “bit level” of Mystic, so if you are using a 32-bit version of Mystic you should install the 32-bit version of Python. If you are using the 64-bit version of Mystic you should install the 64-bit version of Python. Be particularly careful when selecting your installation download in Windows!

In Windows, Python needs to be installed by downloading it from the Website:www.python.org

Most Linux desktop distributions and MacOS will come with Python 2.7 installed by default, and in some cases full Mystic Python functionality will work out of the box without additional steps. However some of the more popular installations such as Ubuntu and Mint Linux do not come with Python installed with shared libraries enabled, which means it will not work with embedded Python applications like Mystic.

If you are using a Linux operating system with this issue then modules such as “sqlite3” will fail when they are included in a script with an error mentioning Py_ZeroStruct. In order to fix this issue, a new Python will have to be compiled in a way that is compatible with Mystic. See the Troubleshooting section below for steps to compile and install Python properly.

Library Validation / Installation

When initializing Python, Mystic will be attempting to locate the following library depending on operating system:

Windows: python27.dll
Linux: libpython2.7.so.1.0
MacOS: libpython2.7.dylib

In Windows, you should probably know if Python is installed already since it has to be manually installed.

In Linux environments, you can usually determine if Python is installed by executing “python –version” in a terminal window. The version should be 2.7.

You can check to see if you have the proper library installed by searching the results of ldconfig:

ldconfig -p | grep libpython2.7.so.1.0

Note that some Linux distributions come with a Python 2.7 package or installation that is compiled in a way that does not work well with embedded Python applications. For more information regarding this and how to fix it, see the Troubleshooting section below.

If the above command does not find anything but “python –version” prints 2.7, then you may have Python installed under a different library name. Execute the same command with just the base library name to locate where Python is installed:

ldconfig -p | grep libpython

The result will tell you where Python 2.7 is installed. If Python 2.7 is installed under a different library name, then you will need to create a symbolic link to that filename using “libpython2.7.so.1.0” so Mystic can find it.

If you cannot locate libpython2 then it may be that you do not have Python 2 installed or that you have a partial installation of Python 2. You will likely need to install Python 2.7 and then possibly create a symbolic link as described above. This can typically be installed by a package manager, as shown below on a Raspbian installation:

sudo apt-get update
sudo apt-get install libpython2.7

Environment Variables

In addition to the basic Python installation, some environment variables may need to be set so that Mystic can find and import 3rd party modules used within your Python programs. In many cases the default installation will work just fine and no modifications will be needed. However, if an error occurs when executing modules, then the environment variables may need to be set or adjusted.

One common error reported when the environment variables need adjusted or set is the message “Importerror: No module named site” printed to STDOUT.

PYTHONHOME and PYTHONPATH are two environment variables which need to be set. Depending on your operating system, Python may already be installed and working without making any changes. As an example, if you have Python installed to C:\PYTHON27 in Windows, you'd want to set environment variables as such:

 SET PYTHONHOME=C:\PYTHON27
 SET PYTHONPATH=C:\PYTHON27\LIB
 SET PATH=%PYTHONHOME%;%PATH%

For more information on how to set environment variables, you'll need to research the specific operating system that you are using and the Python documentation. For reference: Here is what the Python documentation says about these environment variables:

   PYTHONHOME
  
   Change the location of the standard Python libraries. By default, the
   libraries are searched in prefix/lib/pythonversion and
   exec_prefix/lib/pythonversion, where prefix and exec_prefix are
   installation-dependent directories, both defaulting to /usr/local.
  
   When PYTHONHOME is set to a single directory, its value replaces both
   prefix and exec_prefix. To specify different values for these, set
   PYTHONHOME to prefix:exec_prefix.
  
   PYTHONPATH
  
   Augment the default search path for module files. The format is the same
   as the shell’s PATH: one or more directory pathnames separated by
   os.pathsep (e.g. colons on Unix or semicolons on Windows). Non-existent
   directories are silently ignored.
  
   In addition to normal directories, individual PYTHONPATH entries may
   refer to zipfiles containing pure Python modules (in either source or
   compiled form). Extension modules cannot be imported from zipfiles.
  
   The default search path is installation dependent, but generally begins
   with prefix/lib/pythonversion (see PYTHONHOME above). It is always
   appended to PYTHONPATH.
  
   An additional directory will be inserted in the search path in front of
   PYTHONPATH as described above under Interface options. The search path
   can be manipulated from within a Python program as the variable sys.path

Troubleshooting

For more information, read the documentation above.

Windows

The most common Windows issue is that the wrong version of Python is installed. It is absolutely a requirement that you download the 32-bit version of Python if using 32-bit version of Mystic, and the 64-bit version of Python if using the 64-bit version of Mystic.

If you get an error similar to ““Importerror: No module named site” when your script tries to import a module, this means you need to set your Python environment variables. See the section above for information and an example of how to do this in Windows.

Unix

The most common issue in Unix based platforms is that a link is not created to the Python library. Mystic expects to find “libpython2.7.so.1.0” on Linux and “libpython2.7.dylib” in macOS, so if your Python library is stored under a different name then you need to make a symbolic link.

Like the Windows version, another issue some people have ran into is that their bit level of Python does not match that of Mystic which can cause crashes when a script is attempting to execute. The issue seems more prominent in macOS where the owner may not be aware of their OS bit-level, or their OS has a mix and match of 32-bit and 64-bit software and it is not clear what version they should be using.

NOTE: Some Linux distributions come with a pre-installed Python 2.7 or a package-based install of Python 2.7 that is not compiled in a way that works properly with embedded Python applications.

When Python is compiled wrong, it will have issues loading some modules resulting in an error when you execute the Mystic Python script. One of the most popular operating systems (Ubuntu) unfortunately seems to suffer from this problem, and the only way to solve it is to recompile Python 2.7 properly. The enable-shared option is required for embedded applications, and also the unicode size may need to be either ucs2 or ucs4.

The following steps can be used to reinstall Python 2.7 tested on a fresh Ubuntu 18.04 LTS:

INSTALL PREREQUISITES:

  • sudo apt-get update
  • sudo apt-get install build-essential checkinstall
  • sudo apt-get install libreadline-gplv2-dev libncursesw5-dev libssl-dev libsqlite3-dev tk-dev libgdbm-dev libc6-dev libbz2-dev

COMPILE PYTHON:

python_install.txt · Last modified: 2019/03/10 10:18 by g00r00