[Part-1]Linux Python 3 environment

[snippsat]

This will be similar to starting Python in Windows Part-1 Part-2.
The main focus will be running Python 3.5 or higher on Linux.
It's a open tutorial,so if someone has useful information post it here.

I have tested with Mint 18.1 and Ubuntu 16.04(run at Digital Ocean).
Both of these Distros come with Python 3.5 as default Python 3 version.

Basic install:

Output:
sudo apt-get update
sudo apt-get install build-essential
sudo apt-get install python3-dev
sudo apt install python3-pip
sudo pip3 install virtualenv

Testing version:

mint@mint ~ $ python3 -V
Python 3.5.2
mint@mint ~ $ python -V
Python 2.7.12

mint@mint ~ $ pip3 -V
pip 9.0.1 from /usr/local/lib/python3.5/dist-packages (python 3.5)

# Upgrade pip
mint@mint ~ $ pip3 install -U pip
Requirement already up-to-date: pip in /usr/local/lib/python3.5/dist-packages

Running script with Python 3.5 and install with pip3:

# Running code
mint@mint ~ $ python3 hello.py
hello world

# Install Requests
mint@mint ~ $ sudo pip3 install requests
Collecting requests
  Downloading requests-2.14.2-py2.py3-none-any.whl (560kB)
    100% |████████████████████████████████| 563kB 1.1MB/s 
Installing collected packages: requests
Successfully installed requests-2.14.2

# Test that Requests work
mint@mint ~ $ python3
Python 3.5.2 (default, Nov 17 2016, 17:05:23) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import requests
>>> r = requests.get('https://www.python.org/')
>>> r.status_code
200
>>> r.encoding
'utf-8'
>>> r.headers['date']
'Sun, 21 May 2017 13:42:43 GMT'

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PIP
The tool for installing Python packages from PyPi or GitHub,BitBucket and more.

Useful commands:

Output:
pip help (show commands)

# Install and uninstall into Python
pip install requests
pip uninstall requests

# Wheel(.whl) 
pip install some_package.whl
pip uninstall some_package.whl
--- Diffrent ways ---
pip install git+https://github.com/cherrypy/cherrypy.git
pip install -r requirements.txt # A demo later

# Upgrade pip
pip3 install -U pip
# Show version
pip -V 

# Show installed packages 
pip list 
pip freeze

# search PyPi for packages with term "flask" in it 
pip search flask

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Virtual environment
The main purpose of Python virtual environments is to create an isolated environment for Python projects.
This means that each project can have its own dependencies, regardless of what dependencies every other project has.
These dependencies can be written to a requirements.txt which we look at later.

Did install it first in post sudo pip3 install virtualenv
From Python 3.6 will be build in,for Python 3.5 using 3-party Virtualenv.

# Make virtualenv that use Python 3.5
mint@mint ~/Desktop/my_env $ virtualenv -p /usr/bin/python3.5 my_env
mint@mint ~ $ cd my_env

# Activate virtualenv
mint@mint ~/Desktop/my_env $ source bin/activate

# Check python loaction
(my_env) mint@mint ~/my_env $ which python
/home/mint/my_env/bin/python

# pip version
(my_env) mint@mint ~/my_env $ pip -V
pip 9.0.1 from /home/mint/my_env/lib/python3.5/site-packages (python 3.5)

Running this code find_title.py in virtual environment.
So need to install BeautifulSoup, Requests, lxml into virtual environment.

# find_title.py
import requests
from bs4 import BeautifulSoup

def find_title(url):
    url_get = requests.get(url)
    soup = BeautifulSoup(url_get.content, 'lxml')
    print(soup.select('head > title')[0].text)

if __name__ == '__main__':
    #url = 'http://CNN.com'
    url = 'https://www.python.org/'
    find_title(url)

(my_env) mint@mint ~/my_env $ pip install beautifulsoup4 requests lxml
Collecting beautifulsoup4                                                       
Downloading beautifulsoup4-4.6.0-py3-none-any.whl (86kB)                                   
    100% |████████████████████████████████| 92kB 821kB/s 
Collecting requests                                                                              
  Downloading requests-2.14.2-py2.py3-none-any.whl (560kB)                                            
    100% |████████████████████████████████| 563kB 1.2MB/s 
Collecting lxml                                                                                               
  Downloading lxml-3.7.3-cp35-cp35m-manylinux1_x86_64.whl (7.1MB)                                             
    100% |████████████████████████████████| 7.1MB 233kB/s 
Installing collected packages: beautifulsoup4, requests, lxml
Successfully installed beautifulsoup4-4.6.0 lxml-3.7.3 requests-2.14.2

Running code:

Output:
(my_env) mint@mint ~/my_env $ python3 find_title.py
Welcome to Python.org

Make requirements.txt for this virtual environment.

(my_env) mint@mint ~/my_env $ pip freeze > requirements.txt
(my_env) mint@mint ~/my_env $ cat requirements.txt
appdirs==1.4.3
beautifulsoup4==4.6.0
lxml==3.7.3
packaging==16.8
pkg-resources==0.0.0
pyparsing==2.2.0
requests==2.14.2
six==1.10.0

So we see which version that are used,
if something break in future we can now see that with these versions it did work.
Can also install with it.
pip install -r requirements.txt

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Overview image:
[Image: 7KAU5q.jpg]