Learning in a hard way

numpy.array

When creates a numpy.array a = numpy.array([1,2,3]). It is 1-dimensional if not specified. The shape of a can be checked out by a.shape, and it will output (3,).

The number of dimensions will be transformed from 1 to 2 by exploting

a1 = a.reshape(1,3), giving an output array([[1,2,3]])
a2 = a.reshape(3,1), giving an output

array([[1],
       [2],
       [3]])

array.sum

array.sum(axis=0): sum up along the column

a1.sum(axis=0)
#output: array([1, 2, 3])

a2.sum(axis=0)
#output: array([6])

array.sum(axis=1): sum up along the row

a1.sum(axis=1)
#output: array([6])

a2.sum(axis=1)
#output: array([1, 2, 3]) -> 1D array?

a.sum(axis=1) and a.sum(axis=0) give the same output array([6]) because of only one dimension.

Easy coding

´x = x + 1´ is qual to ´x += 1´

Virtualenv - virtual environment manager

venv for Python 3 or virtualen for Python 2

Installing packages using pip and virtual environments

Installing venv

This is how I did for my "Energy-data" project:

Copy the following code into "init_py.sh" file

#!/bin/bash
set -e

PYTHON_ENV_NAME=venv

pip3 install virtualenv

# or 'sudo pip3 install virtualenv'

virtualenv -p python3 $PYTHON_ENV_NAME

echo "source $(pwd)/$PYTHON_ENV_NAME/bin/activate" > .env

source $(pwd)/$PYTHON_ENV_NAME/bin/activate # activate the local python environment

pip3 install jupyter
pip3 install matplotlib
pip3 install pandas
pip3 install scipy
pip3 install seaborn
pip3 install graphviz
pip3 install scikit-learn

echo -e "\n"
echo "Please run \"$ source $PYTHON_ENV_NAME/bin/activate\" to switch to the python environment."
echo "Use \"$ deactivate\" anytime to deactivate the local python environment if you want to switch back to your default python."
echo "Or install autoenv as described on project readme file to make your life much easier."

Other easy ways to do

Video source from Corey Schafer

Text insruction

Note