1.4. Python Language

Figure 1.1. Python Logo

1.4.1. Rationale

• Turing complete, general purpose language

• Multi platform

• Dynamic typing with automatic memory allocation and GC

• Code readability and simplicity is important

• White space are important

• Everything is an object, but you can write functional code too

• Standard language in Machine Learning and Data Science

• Very good standard system library

• Huge ecosystem of external open source libraries

• Open Source created by non-profit Python Software Foundation

1.4.2. Which Version?

• You should use newest official Python version

• Source: https://devguide.python.org/#status-of-python-branches

• Source: https://www.python.org/downloads/

Table 1.2. Future Versions

Version	PEP	Status	Release	End-of-life	Release Manager
3.11	TBA	future	2022-10-04	TBA	Pablo Galindo Salgado
3.10	TBA	development	2021-10-04	TBA	Pablo Galindo Salgado

Table 1.3. Currently Supported Versions

Version	PEP	Status	Release	End-of-life	Release Manager
3.9	PEP 596	features	2020-10-05	TBA	Łukasz Langa
3.8	PEP 569	features	2019-10-20	2024-10	Łukasz Langa
3.7	PEP 537	bugfix	2018-06-27	2023-06-27	Ned Deily
3.6	PEP 494	security	2016-12-23	2021-12-23	Ned Deily

Table 1.4. Unsupported Versions

Version	PEP	Status	Release	End-of-life	Release Manager
3.5	PEP 478	end of life	2015-09-13	2020-09-13	Larry Hastings
3.4	PEP 429	end of life	2014-03-16	2019-03-16	Larry Hastings
3.3	PEP 398	end of life	2012-09-29	2017-09-29	Georg Brandl
3.2	PEP 392	end of life	2011-02-20	2016-02-20	Georg Brandl
3.1	PEP 375	end of life	2009-06-27	2012-04-09	Benjamin Peterson
3.0	PEP 361	end of life	2008-12-03	2009-01-13	Barry Warsaw
2.7	PEP 373	end of life	2010-07-03	2020-04-20	Benjamin Peterson
2.6	PEP 361	end of life	2008-10-01	2013-10-29	Barry Warsaw

1.4.3. Why not Python 2?

• PEP 373 -- Python 2.7 Release Schedule

• PEP 404 -- Python 2.8 Un-release Schedule

• 2020-04-20 - end of Life for Python 2.7

• Python 2 is no longer developed [1, 2]

• Python 2.7 is the last in 2.x branch, and there won't be Python 2.8

• Python 2.7.18, the last release of Python 2 [3]

1.4.4. Changes in Python 3

• All strings are Unicode

• In Python 3 print() is a function, not a keyword

• Changes in standard library modules naming and location

• New string formatting

1.4.5. Python Release Cycle

• Since Python 3.9: PEP 602 -- Annual Release Cycle for Python

• 12 months (1 year) release cycle

• 18 months (1.5 year) of bugfix updates

• 42 months (3.5 year) of security updates

Figure 1.2. Python 12 months release cycle.

1.4.6. Scripts

• Python files use .py as an extension

• Compiled files are in __pycache__ directory

• Python also uses other extensions

Table 1.5. Python file types and extensions

Extension	Description
.pyc	Compiled source code (bytecode)
.pyd	Compiled Windows DLL file
.pyw	Compiled Windows file. Executable with pythonw.exe
.pyx	cPythona source for C/C++ conversion
.pyz	zipapp compressed archive

1.4.7. Python Console (REPL)

• Read–Eval–Print Loop

• Quickly test and evaluate code

• Lines starts with >>>

• Line continuation starts with ...

• Result is printed below

• Open REPL with python3 command in terminal

$ python3
3.8.2 (default, Mar 11 2020, 00:29:50)
[Clang 11.0.0 (clang-1100.0.33.17)]
Type "help", "copyright", "credits" or "license" for more information.

>>> print('Ehlo World!')
Ehlo World!

In documentation and books you may find >>> and ... at the beginning of code listing lines

>>> if True:
...     print('yes')
... else:
...     print('no')
yes

1.4.8. Jupyter

• Open Source web application REPL

• Very popular in Machine Learning and Data Science world

• Create and share documents that contain live code, equations, visualizations and narrative text

• Uses include: data cleaning and transformation, numerical simulation, statistical modeling, data visualization, machine learning, etc

1.4.9. Python Developer Survey

• Annual survey

• https://www.jetbrains.com/lp/python-developers-survey-2020/

• https://www.jetbrains.com/lp/devecosystem-2020/python/

• https://www.jetbrains.com/lp/python-developers-survey-2019/

• https://www.jetbrains.com/research/python-developers-survey-2018/

• https://www.jetbrains.com/research/python-developers-survey-2017/

• https://insights.stackoverflow.com/survey/2020

• https://insights.stackoverflow.com/survey/2019

• https://insights.stackoverflow.com/survey/2018

1.4.10. Assignments

Code 1.8. Solution

"""
* Assignment: About Environment
* Complexity: easy
* Lines of code: 0 lines
* Time: 3 min

English:
    TODO: English Translation

Polish:
    1. Stwórz plik o nazwie `about_env.py`
    2. Użyj danych z sekcji "Given" (patrz poniżej)
    3. Uruchom plik w swoim IDE (menu `Run -> Run... -> nazwa Twojego skryptu`)
    4. Gdzie Python jest zainstalowany?
    5. Czy korzystasz z "Virtualenv"?
    6. Upewnij się, że w linijce z "Virtualenv" nie masz `None`

Tests:
    >>> assert python_executable is not None
    >>> assert python_version is not None
    >>> assert venv is not None
"""


# Given
import sys
import os


python_executable = sys.executable
python_version = tuple(sys.version_info)
venv = os.getenv("VIRTUAL_ENV")