Mod:Hunt Research Group/python

Using python on your mac

• there are many options for using python on your mac (see below)
• sometimes codes will only work with a specific version of python

using python

• cd into directory where the py file is
• to run a python script type

python script.py

• to exit python type (Control-D)
• find out what version you have active: "python -V" or "python --version"
• python -c “commands” [arg] executes commands

installing python as a stand alone

• there are 2 main versions of python, python2.7 and python3.5 (currently)

you will likely want both

• use MacPorts to download python

sudo port search --name --line --glob 'python*'

sudo port installed 'python*'

sudo port select --list python

sudo port install python37

port select --set python python37

sudo port install python 27

port select --set python2 python27

• you could also add an alias to your .bashrc file

alias python37=“/opt/local/bin/python3.7”

• to ensure the macports version is used

in your $PATH make sure /opt/local/bin occurs before /user/bin

to find out what version you have active: "python -V" or "python --version"

installing python libraries

• and actually you should go the whole hog with science based libraries

sudo port install py37-numpy py37-matplotlib py37-scipy py37-pandas py37-pip  py37-fortranformat 

• matplotlib is a python 2d plotting library http://matplotlib.org
• scipy is a python package of software for mathematics science and engineering http://scipy.org
• fortranformat reads variables according to fortran format statements https://pypi.python.org/pypi/fortranformat

• you can also install with pip

NOTE: "pip" will only install 2.7 version of packages

pip install matplotlib scipy fortranformat

use pip3.x with versions of python

pip3.5 install matplotlib scipy fortranformat

• possible issue found in 2018

pip3 --version delivers 3.5 and not 3.7

which pip shows /opt/local BUT pip3 shows /usr/local

so pip3 is from the wrong installation of python

sudo port select --set pip pip27 works BUT sudo port select --set pip3 pip37 fails!

so force the use of python3: sudo -H python3 -m pip install .

version active

• NOTE there can be problems with which version is called, even once python is set using macports

the Mac (Mojave) has a preinstalled version of python in /user/bin

the Mac (Sierra) has a preinstalled version of python in /user/local/bin

python.org installs in /Library/Frameworks/Python.framework/Versions/3.5/bin

macports installs in /opt/local/bin

to find out which version is being used type "which python"

to find out the version of python used "python -V":or "python --version"

to ensure the macports version is used in your $PATH make sure /opt/local/bin occurs before /user/bin

sometimes other initiating files add things to your path, so key an eye on this variable

choose in what order to search the relevant directories

for example

   export PATH="/opt/local/bin:/opt/local/sbin:$PATH"
   export PATH=$PATH:/Users/$USER/bin
[tricia@clove]/Users/tricia $ echo $PATH
/opt/local/bin:/opt/local/sbin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/tricia/bin
[tricia@clove]/Users/tricia $

using a prepackaged environments

• are often favoured by students
• download mac version of Anaconda mac

useful link http://www.southampton.ac.uk/~fangohr/blog/installation-of-python-spyder-numpy-sympy-scipy-pytest-matplotlib-via-anaconda.html •to check things are working run the code check_python.py ....

• anaconda can be activated graphically from your Applications folder, click on Anaconda-Navigator.app
• you want to activate spyder so click on the "launch" button
• a large window will appear ....
• spyder is the programming environment