Python Tutorial Link to heading

Resource: https://docs.python.org/3/tutorial/index.html

Overview Link to heading

At first glance this teaches about:

  • Basics: variables, operators and data types. Math, numbers, strings and lists
  • Flow structures: if, for, while loops. break/continue
  • Functions
  • Data structures: lists, dicts, sets, tuples
  • Modules, Packages and Classes
  • Most popular libs: math, random, datetime, statistics,
  • Exceptions: try, except, finally
  • Others: List comprehension, function decorators

An Informal Introduction to Python Link to heading

Simplier math operations, variables definition and strings manipulation. Also a little bit of lists. Here an example 🔗 01.lab01.py

More Control Flow Tools Link to heading

Conditionals, Loops, Match/Case, Functions (positional arguments and keywords) and Lambdas.

Data Structures Link to heading

Basics:

  • Lists: its common functions: count, sort, sort, reverse, copy, extend, insert, remove, pop, clear, index
  • Stacks: A list can be treated as stac by using its functions like list.append() or list.pop()
    • Remember a stack is FIFO
  • Queues: By usage of deque from collections
    • Remember a queue is LIFO
  • List comprenhensions: Done by [] with a for loop (the so called list comprehensions) and lambdas
  • Tuples: Immutable items on a list
  • Sets: Unique items on a list
  • Dictionaries: key:value pair of items

Modules Link to heading

A single file becomes a module, for example foobar.py becomes a module called foobar.

The default modules loaded in python are:

  • builtins
  • os and sys but partially, not all its functions/features

❗ Important to keep in mind that if a single py file is executed directly it becomes __name__ = __main__ but if it is being called from another py file then __name__ becomes the name of the py file (see lab04 py scripts on this repo).

Modules are loaded from sys.builtin_module_names or sys.path (PYTHONPATH, current directory or site-packages dir).

The dir() function lists all available properties and functions of a given module, e.g.: dir(sys) or dir(builtins)

Packages 📦 are sub-directories of a module for example this package sounds.effects.echo has this path directory: ./sounds/effects/echo.py we can import it like from sounds.effects import * or relatively load the module from ..sounds.effects import *.

Input and Output Link to heading

What python can offer are basically ways to output data say strings or numbers to output resources like the terminal itself also read-write to files.

Formatting:

  • f'Results of the {year} {event}'
  • '{:-9} YES votes {:2.2%}'.format(yes_votes, percentage)
  • Usage of repr() and str()
  • f'The value of pi is approximately {math.pi:.3f}.'
  • print('{0:2d} {1:3d} {2:4d}'.format(x, x*x, x*x*x))
  • '12'.zfill(5) for numbers

Files:

  • with open('workfile', encoding="utf-8") as f:... by default mode is r
  • import json, json.load(f), json.dump(object_structured, f)

Errors and Exceptions Link to heading

  • Common exceptions: OSError, ValueError, Exception, KeyboardInterrupt
  • finally block is processed regardless if try/execpt blocks were processed
  • else block is processed only when the try block was successful

Classes Link to heading

  • By default all variables are defaulted to local scope.
    • A del foobar removes the binding from the namespace referenced by the local scope
    • global: is a variable defined inside a function that can be modified externally, globally
    • nonlocal: is a variable that belongs in the nearest eclosing scope and its not global, but can be modified on any inner function
  • A class has to be initiated with function __init__(self, foo, bar):
  • Classes support Inheritance and Multiple Inheritance

Brief Tour of the Standard Library Link to heading

Popular standard py libraries: os shutil glob sys argparse re math random statistics urllib date

Brief Tour of the Standard Library — Part II Link to heading

Popular standard libs: reprlib, pprint, textwrap, locale, Template, struct, threading, logging, array

Virtual Environments and Packages Link to heading

Some notes Link to heading

Creator of this language is Guido Van Rossum, his main intention (besides a hobby project), was to create a programming language for everybody, literally that was his motivation and vision. I think he made it!.

From wikipedia:

In 1999, Van Rossum submitted a funding proposal to DARPA called “Computer Programming for Everybody”, in which he further defined his goals for Python.

Python 2 vs Python 3! 🥊 Link to heading

This was done mainly to get a better maintenability of the code, lots of redundancies removed, code improved. But also breaks compatability.

Visibible from user developer perspective (?):

  • No parenthesis for prints
  • Float numbers for integer division
  • All is Unicode
  • Improved iterators (range(), dict.keys())
  • Standard libraries reorganized
  • Error handling refactoring