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python_install

Python

Installation and Requirements

Mystic requires that Python 2.7 is installed on your system if you wish to execute Python scripts. The presence of Python is detected automatically by Mystic, and is initialized as needed. It is not in any way a dependency and Mystic will continue to operate normally without it should you decide you do not wish to use it.

Most Linux desktop distributions and Apple's macOS will come with Python 2.7 installed by default, and in many cases no installation will be required in order to use Python. If not, it can typically be installed by a package manager in Unix (explained below). In Windows, Python needs to be installed by downloading it from the Website: www.python.org

Note: If you are using the 32-bit version of Mystic (even if it is in a 64-bit operating system), then you need the 32-bit version of Python installed. If you are using the 64-bit version of Mystic then you need to have the 64-bit version of Python installed. This is a very common mistake, particularly on the Windows platform where SysOps will download the wrong bit-version of Python.

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

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

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.

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.

python_install.txt · Last modified: 2018/01/01 15:50 by g00r00