pages tagged Python

Python division

Tue, 16 May 2017 23:59:39 +0000

In Python 2, dividing two integers will yield a rounded integer result:

$ ipython2
Python 2.7.11 (default, Jan 22 2016, 08:29:18)
Type "copyright", "credits" or "license" for more information.

IPython 4.1.2 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: 1/2
Out[1]: 0

To get a real-number result:

In [2]: 1./2
Out[2]: 0.5

In [3]: float(1)/2
Out[3]: 0.5

In Python 3, the default is the real-number result:

$ ipython
Python 3.5.1 (default, Dec  7 2015, 21:59:10)
Type "copyright", "credits" or "license" for more information.

IPython 4.1.2 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [2]: 1/2
Out[2]: 0.5

In [3]: exit
>>> elapsed time 15s

In a Python script, to use Python 3 division behavior for Python 2:

import from __future__ division;
print 1/2

How to use matplotlib in Python virtual envrionments

Tue, 16 May 2017 23:59:39 +0000

backend: TkAgg

References

http://matplotlib.org/faq/virtualenv_faq.html

Installing and configuring Python on Ubuntu Linux

Tue, 16 May 2017 23:59:39 +0000

Install system packages

sudo apt-get install gfortran libopenblas-base libopenblas-dev libzmq3-dev
sudo apt-get install python-qt4 python-zmq

The following shew up as dependencies when I tried to install matplotlib in a virtual environment using pip install matplotlib:

sudo apt-get install libfreetype6-dev libpng12-dev

Install Python

sudo apt-get install python python-pip python-dev build-essentials
sudo apt-get install python3 python3-pip

Install IPython

sudo apt-get install ipython python-notebook

To install IPython with Python 3 [¹]:

sudo apt-get install ipython3 python3-notebook

Install Python packages

Use Ubuntu's package management system `apt-get`:

sudo apt-get install python-matplotlib
sudo apt-get install virtualenv vurtualenvwrapper

Use Python package management system `pip`:

pip install "ipython[all]"
pip install virtualenv
pip install virtualenvwrapper
pip install numpy
pip install scipy
pip install matplotlib
pip install pyzmq
pip install pygments

Use Anaconda Python distribution and its package management and environment management

This part is same on macOS or Ubuntu Linux. See installing and configuring Python on macOS.

Other packages

GraphLab, a machine-learning package

This part is same on macOS or Ubuntu Linux. See installing and configuring Python on macOS.

References

It used to be that ipython has to be installed via pip3, but I think this has been superseded by the above as of Ubuntu 15.10 and Mar. 2016 at least:

pip3 install ipython
↩

Installing and configuring Python on macOS

Tue, 16 May 2017 23:59:39 +0000

History

2016-3: Tested on macOS 10.11.3

Install other softwares

Install XQuartz.
Install MacTeX.
Install Home brew.
Install Xcode and command-line tools.
```
  xcode-select --install
```

Include only the necessary paths in $PATH:

  bash$ echo $PATH
  /usr/local/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/Library/TeX/texbin:/usr/X11/bin:/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin

Install packages

brew install cmake

Install Python

Make sure you start from a clean and error-free state with Homebrew:
```
  brew doctor
```

Check outdated packages:

    brew outdated

Update:

    brew update
    brew upgrade

Add additional repositories and re-check:

    brew tap homebrew/science
    brew tap homebrew/python
    brew doctor
    brew update 
    brew upgrade
    brew doctor

Install Python:

  $ brew install python python3
  $ which python
  /usr/local/bin/python
  $ python --version
  Python 2.7.11
  $ which python3
  /usr/local/bin/python
  $ python3 --version
  Python 3.5.1

This actually also installs the package management system pip:

  $ which pip
  /usr/local/bin/pip
  $ which pip3
  /usr/local/bin/pip3

Install other system packages

    brew install libtiff 
    brew install libjpeg 
    brew install webp 
    brew install py2cairo
    brew install cairo
    brew install little-cms2
    brew install imagemagick --with-fftw --with-librsvg --with-x11
    brew install graphviz --with-librsvg --with-x11
    brew install qt pyqt
    brew install zmq
    brew install zeromq
    brew install gcc
    brew install freetype

Install Python packages

Warnings: * For the same software or library, install once using brew install <package> or pip install <package> but not both. The latter is usually more up-to-date. * Do not use sudo pip.

Install with `brew`

    brew install homebrew/python/matplotlib --with-cairo --with-tex

Alternatively, install with `pip`

Update:

  pip install --upgrade pip
  pip install pip-review
  pip3 install --upgrade pip
  pip3 install pip-review

Virtual environment:

  pip install virtualenv
  pip install virtualenvwrapper

IPython

  pip install "ipython[all]"
  pip3 install "ipython[all]"

Start IPython notebook server by:

    ipython notebook
    ipython3 notebook

and open http://localhost:8889/tree in Web browser.

Unit testing:
```
  pip install nose
```

Scientific computing:

  pip install numpy
  pip install scipy
  pip install sympy
  python -c 'import numpy ; numpy.test();'
  python -c 'import scipy ; scipy.test();'

Data management:
```
  pip install pandas
```
Natural Language Toolkit
```
  pip install nltk
```

Graphics related:

  pip install snakeviz
  pip install pyzmq
  pip install pygments

For matplotlib choose only one of the following:

    brew install homebrew/python/matplotlib --with-cairo --with-tex
    pip install matplotlib

Others:
```
  pip install q
```

Use Anaconda Python distribution and its package management and environment management

Should I use Anaconda?

Anaconda is itself a Python distribution including Python and lots of Python packages for scientific and technical computing. It also includes a package management system as well as a environment management system. It's fairly popular and convenient to install and use for beginners. But by using pip as the package management system the virtualenv and virtualenvwrapper packages as the environment management system, one can live without Anaconda. Roughly speaking, Anaconda is to Python what stack is to Haskell.

Install Anaconda (see instruction). Put Anaconda bin and man paths in $PATH in ~/.bashrc:

  export PATH=$HOME/anaconda/bin:$PATH
  export MANPATH=$HOME/anaconda/share/man:$MANPATH

Update

    conda update conda
    conda update anaconda

Create a new environment my-env:

  conda create -n my-env python=2.7 anaconda

Activate the environment:
```
  source activate my-env
```

Install and/or update packages:

  conda update conda
  conda update anaconda
  conda update pip
  conda update ipython ipython-notebook

Alternative to Anaconda, set up project-specific Python environment using `virtualenv` and system Python

Let's install specific packages and/or specific versions of some packages in isolated environment named my-env for a specific project.

Create a virtual environment named my-env:

  cd path/to/project
  virtualenv my-env
  git ignore my-env

Activate the virtual environment:

  $ source my-env/bin/activate
  $ echo $VIRTUAL_ENV
  /Users/meng/project/my-env
  (my-env)

Other packages

GraphLab, a machine-learning package

https://dato.com/download/install-graphlab-create-command-line.html

You can obtain a free 1-year license for educational purposes such as taking the University of Washington Machine Learning course series on coursera.org.

pages tagged Python

Python division

How to use matplotlib in Python virtual envrionments

References

Installing and configuring Python on Ubuntu Linux

Install system packages

Install Python

Install IPython

Install Python packages

Use Ubuntu's package management system apt-get:

Use Python package management system pip:

Use Anaconda Python distribution and its package management and environment management

Other packages

GraphLab, a machine-learning package

References

Installing and configuring Python on macOS

History

Install other softwares

Install packages

Install Python

Install other system packages

Install Python packages

Install with brew

Alternatively, install with pip

Use Anaconda Python distribution and its package management and environment management

Alternative to Anaconda, set up project-specific Python environment using virtualenv and system Python

Other packages

GraphLab, a machine-learning package

References

Use Ubuntu's package management system `apt-get`:

Use Python package management system `pip`:

Install with `brew`

Alternatively, install with `pip`

Alternative to Anaconda, set up project-specific Python environment using `virtualenv` and system Python