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Learn Python Programming Masterclass

https://www.udemy.com/course/python-the-complete-python-developer-course

Progress: 400/(580/100)

Documentation

https://docs.python.org/3.11

IntelliJ python shortkeys:

CMD+\ comment block
CMD+shift+R run code
ALT+CMD+L reformat code

Section 2: Install and Setup

Q: Is it better to use vanilla python or a distribution like anaconda? We need to use a package to interface with hardware which is a Python extension to a C library (harvesters). It also requires specific Python versions. A: TBD

Using Combination of vanilla python and IntelliJ IDE from Jetbrains. Community edition
Virtual environements for dependency management so you don't screw up your python main installation. virtualenv venv.
Venv could be suffixed with python version e.g venv-python39 or venv\python39
Manage virtual envs from -> File -> Project structure -> Platform settings -> SDKs
Conda is an alternative for virtualenv
IntelliJ supports markdown and PlantUML/Mermaid diagrams and HTML preview
IdeaVim emulation for vim users -> make it comfy

Could also install PyCharm. Pycharm is same applicable as python plugin for IntelliJ IDEA

Section 3: Stepping into the World of Python

Code format according to PEP 8?

Python 2 EOL since 2019, focus on 3

16. Printing in Python

A function has a specific amount of arguments, but can have variable list of arguments. The print function is made to have variable list of arguments. The print function by defaults adds spaces in the output for multi-argument prints and a newline.

In Python all functions return a value.

Q: What about pprint.pprint for debugging? A: TBD

Exercise: Print text conditionally using ternary operator:

IsFull = True

print("My hovercraft is", "full" if IsFull else "not full", "of eels")

17. Strings in Python

Q: Multiple string types '' and "" and r"" ?

In Python 3 all strings are unicode formatted. In Python 2 strings need to be prefixed with u"". See also https://docs.python.org/2/howto/unicode.html#unicode-literals-in-python-source-code

Section 5 Lists and Typles

Lists

A sequence is an ordered collection of items, the word ordered is important. Something that can be looped over with for is iterable. The accurate definition of an iterable is that an object contains either the __iter__ or __getitem__ method. All sequence types can be iterated over, strings, lists etc are iterable types. Not all iterables are sequences.

Lists are mutable, strings are immutable

Immutable objects

Python immutable types, things which can not be changed:

int
float
bool (subclass of int)
str (string)
tuple
frozenset
bytes

id gets the id of an object is guaranteed to be unique and constant for the object lifetime. the Cpython implementation does return the object memory address

Mutable objects

list
dict
set
bytearray

Operations on Mutable Sequences

https://docs.python.org/3/library/stdtypes.html#mutable-sequence-types

E.g append method. A method is bound to an object a function is not. A function is e.g min or max. Dot notation e.g list s append object x is written as s.append(x). Dot notation is used in a lot of object oriented programming.

Iterate over a list

Using for with sequence.index(item) is not good for performance. We must use enumerate to get the index and the item.

Python list comprehension:

letters = [letter for letter in 'human']

Section 6 Functions an introduction

Docstrings

Docstrings are the documentation for functions. They are an attribute of the function. And can be accessed using .__doc__ or builtin help.

"""

"""

Typehints and annotations

Example:

def myfunction(x: int = 0) -> bool:
	return False

Virtual Environment

To activate execute activate(.bat) on windows or source activate on *nix.

Testing and debugging

Testing is the process of finding out if there are bugs in your code
Debugging is the process of working out what the bugs are, and fixing them

Section 7 Dictionaries and Sets

setdefault

if item_name in shopping_list:
	# Item is already in the list, so we need to buy more
	shopping_list[item_name] += item_quantity
else:
	shopping_list[item_name] = item_quantity

# code reduction by use the list setdefault function
shopping_list[item_name] = shopping_list.setdefault(item_name, 0) + item_quantity

check if list is empty or not

l1 = ["Hire", "the", "top", "1%", "freelancers"]

l2 = []

if l2:
    print("list is not empty")
else:
    print("list is empty")

#Output: "list is empty"

Introduction to sets

A set is an unordered collection with no duplicate entries. Python has builtin set.

https://docs.python.org/3.11/library/stdtypes.html#set

Set operations

Set union -> removes duplicates

set1.union(set2) # or
set1 | set2

Set intersection -> get common items

set1.intersection(set2) # or
set1 & set2

Set difference -> substracts common items

set1 - set2 # or:
set1.difference(set2)

Symmetric difference -> reverse of intersection, removes common items

set1 ^ set2 # or:
set1.symmetric_difference(set2)

Subsets and supersets

Use operators <, <=, > and >=

Misc tips and tricks

Convert datetime string to object

from datetime import datetime

datetime_str = '09/19/22 13:55:26'

datetime_object = datetime.strptime(datetime_str, '%m/%d/%y %H:%M:%S')

print(type(datetime_object))
print(datetime_object)  # printed in default format

Pretty print JSON string

Set the indent of json.dumps:

import json

json_data = '[{"ID":10,"Name":"Pankaj","Role":"CEO"},' \
            '{"ID":20,"Name":"David Lee","Role":"Editor"}]'

json_object = json.loads(json_data)

json_formatted_str = json.dumps(json_object, indent=2)

print(json_formatted_str)

Class equivalence

You need to be careful with inheritance:

>>> class Foo:
    def __eq__(self, other):
        if isinstance(other, self.__class__):
            return self.__dict__ == other.__dict__
        else:
            return False

>>> class Bar(Foo):pass

>>> b = Bar()
>>> f = Foo()
>>> f == b
True
>>> b == f
False

Check types more strictly, like this:

def __eq__(self, other):
    if type(other) is type(self):
        return self.__dict__ == other.__dict__
    return False

Besides that, your approach will work fine, that's what special methods are there for.

See https://stackoverflow.com/questions/390250/elegant-ways-to-support-equivalence-equality-in-python-classes

Chapter 8 read-writing files in Python

Python 3 string type is native UTF-8. When the open builtin function is called an explict encoding can be given which is more portable between operating systems.

Intellij file encoding

View -> Appareance -> Status bar widgets -> File encoding

Then the status bar get this file information:

File encoding in python

https://docs.python.org/3/howto/unicode.html https://docs.python.org/3/library/codecs.html?highlight=codecs%20file%20encoding#standard-encodings

Data serialization

E.g JSON, CSV data formats

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