Well Grounded Python Coding - Revision 1 (Day 1 Slides)

1 WELL-GROUNDED PYTHON CODING Worajedt Sitthidumrong Class #1 - Dec 21-22, 2019 www.qython.io Copyrights 2019 by Worajedt Sitthidumrong. For your Personal Uses Only.

2 BASIC https://learnxinyminutes.com/docs/ python3/ (ภาษาไทยกำลังมาในไม่ช้า) Pareto Principle 80:20

3 EX01 DATA TYPES & STATEMENT Data types •Basic [int, ﬂoat, boolean, string, char] •Complex [set, tuple, list, dict] •type() Coding Language •Comment •Assignment •Expression •Blocks (if, loop)

4 EX01 DATA TYPES & STATEMENT (CONT.) Equality •Is Operator •Assigned to •== •!= Caution! •Variable and naming •Indents •Common Errors

5 EX02 VIRTUAL ENVIRONMENT Why you should use ‘virtual environment’? •What is venv •How to conﬁg and use venv in PyCharm •How many of them? •virtualenv •conda •pipenv

6 EX03 PACKAGE INSTALLATION What is ‘pip’ •pip search …… •pip install …… •pip freeze > requirements.txt •pip install requirements.txt

7 MATH Very primitive operators that you must know how to use them. + - * / % // **

8 EX01 MATH CALC 1 Write a program that calculate ‘Area of Square, Rectangle, Triangle’ •Use this formulas [ w * w, w * h, 1/2 * b * h ] •Note about integer or ﬂoat calculation. Write a program that calculate ‘VAT’ •Use this calculation [ taxed_price = price + ( 7% of price) ] Rewrite them again with ‘input()’ •Rewrite all programs above with user’s input for [ w, h, b, price ]

9 EX02 MATH CALC 2 DIVISION Write a program ‘Does it Odd?’ •Get one user input and show that it is an odd number or not •Note modulus (%) may be helpful Write a program ‘FizzBuzz’ •Get one user input and consider if it can be divided by 3 or 5 or both without remainder.

10 EX03 MATH CALC 3 PARENTHESIS, ORDER Consider this expressions •print( 100-2/3^5 ) •print( (100-2)/3^5 ) •print( 100-(2/3)^5 ) •print( 100-2/(3^5) ) What make them different?

11 EX04 MATH CALC 4 ‘MATH MODULE’ Try this ‘math’ module by yourself •math.pi •math.pow() •math.random() Can you explain ‘random()’

12 STRING What you mostly use for human communication and presentation String in many senses; list, chars and know how to transform them

13 EX01 ASCII, UNICODE • CHAR, STRING Do you know ‘ASCII’ or ‘Unicode’ Character Code? •What’s saved in computer when your text has ‘ABCD’ inside? •Note try to ﬁnd which text encoding inside your PyCharm ﬁles. Find out more about ‘ASCII’ and ‘Unicode’ tables •Non-printable characters. [ n, r, t ] ‘Char’ acter and ‘String’ •String made from characters.

14 EX02 STRING OPERATOR What’s possible to calculate with ‘string’? •‘concatenate’ or ‘plus’ •‘in’ & ‘not’ •‘multiply’ ? Really? •len() •upcase(), lowcase() ‘slice’ is BIGGGGGGGG •REMEMBER THIS!! [ string[start:stop:step] ]string[start:stop:step] ‘slice’ is BIGGGGGGGG

15 EX03 STRING FORMAT It’s better to use .format() than multiple plus operators •‘The {} brown fox jumped over the lazy dog’.format(‘quick’) •‘Only {0} lived for others is {0} {1}’.format(‘a life’,’worthwhile’} •# - Albert Einstein •‘Hi {name}, an announcement has been made from {teacher}, instructor of {course} and 2 more courses.’ .format( name=‘Worajedt’, teacher=‘Holczer’, course=‘Advanced Algorithms in Java, Data Structures in Java’ )

16 EX04 STRING FORMAT USE CASE •Can you create a program to print this medication label? •Note : Use keywords to be placeholders instead of numeric index

17 SYSTEM THEORY Do you ever heard of.. Input-Process-Output or.. Garbage in, garbage out? Learn more Learn more

18 BASIC OF ‘SYSTEM THEORY’ Input Output Process Feedback

19 EX01 GRADING FUNCTION Write a program that return grade from input score •Grades are : • Grade Score Range A >= 80 B 70 - 79 C 60 - 69 D 50 = 59 F < 50

20 CONDITION When we have information, it let us ‘make decision’. If-else, if-elif-else and boolean algebra come in.

21 EX01 GRADING REVISIT Enhance your grading system again with if-elif-else •Is it a number ? •Is it within range 0 - 100 ? •Make your code readable •Wrap main idea within •if __name__ == ‘__main__’: • xxxxx • xxxxx

22 EX02 FIZZBUZZ APP REVISIT Enhance your FizzBuzz again with if-elif-else •Is it a number ? •Is it within range 0 - 100 ? •Wrap the main logic within check_ﬁzzbuxz() •Make your code readable •Wrap main idea within •if __name__ == ‘__main__’: • xxxxx • xxxxx

23 Information can hold in a variable. But a variable can hold more than one information. Ordered or Unordered. Set, Tuple, List and Dictionary. All of these come with different kind of parenthesizes. COMPLEX DATATYPES

24 EX01 CREATE LIST VS TUPLELIST What’s the different between ‘tuple’ and ‘list’ ? •Tuple is Read Only & faster •Both are ‘array’ •Both are ‘ordered list’ •Both are ‘zero-based index’ tp = (1,5,7,9) # create a tuple li = [1,5,7,9] # create a list

25 EX02 MODIFY LIST List can be modiﬁed, so these are ways you can do with a list. •Find size of list •Pull data from each list •Add more member(element) •Remove member (one by one) •Reverse all members •Count a selected member •Find index(position) of a member •Find if list has this member LIST

26 EX03 OPERATIONS We can use some operations, check it out. •Combine lists ( and tuple! ) •Unpack members to variables LIST

27 EX04 SLICE List has one thing you must practice, slicing the list LIST list[start:stop:step] 0 1 2 3 4 5 6 7 8 B U T T E R F L Y -9 -8 -7 -6 -5 -4 -3 -2 -1

28 EX05 LIST COMPREHENSION List Comprehension helps you deﬁne members with condition(s) •Create a list consists of members in a condition •You can use condition to create members •And map() object to help you modiﬁed members •Also, you can use this comprehension with ‘tuple’ LIST

29 EX06 LIST OF LISTS (2D ARRAY) Just a simple rules, list can have any types of its member. Even list. •Try to create a simple data made from list of lists •How can we replace the red location? LIST two_d_li = [ [1,3,5,7], [2,4,6,8], [5,0,5,0] ]

30 EX01 CREATE DICT Unordered list of data that comes with pair of {key:value} •They are paired { “key”: value } •No ordered •Access by ‘key’ •Can get a list of keys and a list of values DICTIONARY

31 EX02 MODIFY DICT Dictionary can do mostly list can •You can ﬁnd if the key exists •And avoid error with .get() •Update value and append value DICTIONARY

32 EX01 COMMON STRUCTURE The most important and common structure of ‘database’ •1 Root key (option) •Array (list) at root level •Consists of dictionary (same structure) as the list members Database query result, JSON API result are the most common format like this. LIST OF DICTIONARY

33 EX02 CREATE A JSON DATA Learn how to create a JSON data •What’s JSON? •Try to create a JSON data from your experience LIST OF DICTIONARY

34 FOR LOOP Bunch of information may require the same set of instructions on them. For-loops have many ways to deal with each kind of data types.

35 EX01 FOR LOOP WITH COUNTER ‘for in’ LIST If we deal with ‘ordered list’ , we can use ‘for in’ •for animal in ["dog", "cat", "mouse"]: •for i in range(4): •list = ["dog", "cat", "mouse"] •for i, value in enumerate(list): • print(i, value) •x = 0 •while x < 4: • print(x) • x += 1 # or x = x+1

36 EX02 FOR + IF ELSE FIZZBUZZ REVISIT ‘for in’ LIST Can you modify your FizzBuzz? •Create a list of number, may be from range() •Then apply ﬁzzbuzz() for every items •Print the output

37 EX01 FOOTBALL PLAYERS ‘for each’ DICT Actually, there is NO ‘for each’ in Python. •a_dict = {'one': 1, 'two': 2, 'thee': 3, 'four': 4} •new_dict = {} •for key, value in a_dict.items(): • new_dict[value] = key •print(new_dict) •Now create a dict of football players and iterates over them.

38 EX02 FOR + IF ELSE ‘for each’ DICT You can apply condition to each loop From the dict of football players, now iterates over them, only who are older than 30 yrs

39 EX01-10 : CONTINUOUS EXERCISES RUNNERS Use the exercises 01-10 about runners, complete them all!

40 PYCHARM IDE Do you really know how to use PyCharm IDE? I bet you’re not. Not even close.

41 CODING THE RIGHT WAY Design how your program should work. •Start from main() •Write something readable and not too complex •Create pseudo function and variable then refactor to real one •Alt+Enter | Opt+Return is god send! •Migrate each of them to the right ﬁles/modules •Alt+Enter | Opt+Return is god send!

42 TEXT EDITING To learn a good text editor, learn about this •Cursor movements •Multi-Cursor •Column Selection Mode •Find and Replace •Regular-Expression ( an alien language that save your @$$)

43 REFACTORING Refactoring features in PyCharm you should know •(Watch the demo in class)

44 RUNNING & DEBUGGING In PyCharm you can set many running conﬁgurations. •(Watch the demo in class) PyCharm debug features is much more readable, let’s do it! •(Watch the demo in class)

45 Do you know when your code works? How you measure it? Are you sure your measure tool working correctly? If you’re sure, how long it can be working properly? TDD techniques and testing frameworks help you sleep better. TEST DRIVEN DEVELOPMENT (TDD)

46 WHAT IS TDD? • Do you know when your code works? • How you measure it? • Are you sure your measure tool working correctly? • If you’re sure, how long it can be working properly?

48 ‘pytest’ ‘pytest’ is one of the best testing library in Python • Almost no conﬁguration • Fast running • Many extension, even BDD (Behavior-Driven Development) • Integrate with PyCharm (Professional) Time to demo !

49 EX01 TDD CALCULATOR EX02 TDD AREA CALC EX03 TDD VAT CALC

50 WORKSHOP 01 TDD : FIND A FREE RANGE

51 WORKSHOP 02 TDD : FIND THE RIGHT EAN13 BARCODE CHECK DIGIT https://www.gs1.org/services/how-calculate-check-digit-manually The following table gives an example to illustrate how a GTIN-13 Check Digit is calculated:

52 WORKSHOP 03 TDD : FIND THE RIGHT PERSONAL ID ในการตรวจสอบเลขที่บัตรประชาชนนั้นทำได้โดยการใช้ Check Digit โดยใช้ตัวเลขหลัก สุดท้ายในการตรวจสอบ Algorithm ของวิธีการใช้ Check Digit มีดังนี้ 1.ตัวเลขบนบัตรประชาชนจะมีทั้งหมด 13 หลัก นำเลขใน 12 หลักแรก มาคูณกับเลขประจำ ตำแหน่ง (เลขประจำหลักได้แก่ 13 บวก 1 ลบด้วยตำแหน่งที่) จะได้ตัวเลขประจำตำแหน่ง ดังนี้ 2.หลังจากนั้นเอาผลคูณของทั้ง 12 หลักมารวมกัน แล้วหารเอาเศษด้วย 11 3.เอาเศษที่ได้จากการหารในข้อ 2 มาลบด้วย 11 เท่านี้ก็ได้เลขที่เป็น Check Digit แล้ว (ถ้า ผลจากข้อ 2 ได้ 10 ให้เอาเลขหลักหน่วยเป็น Check Digit ก็คือ 0 นั่นเอง)

53 WORKSHOP 03 TDD : FIND THE RIGHT PERSONAL ID (CONT) ตัวอย่าง 1-2345-67890-12-1 1.นำไปคูณเลขประจำ ตำแหน่ง : (1*13)+(2*12)+(3*11)+(4*10)+(5*9)+(6*8)+(7*7)+(8*6)+ (9*5)+(0*4)+(1*3)+(2*2) = 352 2.หารเอาเศษด้วย : 11 352%11= 0 3.นำ 11 ตั้งแล้วลบเศษที่ได้จากการหารในข้อ 2 : 11 – 0 = 11 (เอาเลข หลักหน่วย) ดังนั้น Check Digit คือ 1 4.จะได้ : 1-2345-67890-12-1

54 WORKSHOP 04 TDD : FIND THE RIGHT ISBN(10) ถ้าเราเอาหนังสืออะไรก็ได้มาหนึ่งเล่มแล้วเปิดไปที่ barcode (น่าจะอยู่ด้านหลัง) ด้านบนของ barcode จะ เป็นคำว่า ISBN และตัวเลขหลายหลัก 1.) เอาตัวเลขหลักแรก คูณ 10 ตัวต่อมาคูณ 9 ตัวต่อมาคูณ 8 ไปเรื่อยๆ จนถึงตัวรองสุดท้าย 2.) เอาผลคูณที่ได้ทั้งหมดมาบวกกัน 3.) เอาผลบวกที่ได้ หารด้วย 11 และดูเศษ เศษที่ได้จะกลายเป็นตัวเลขหลักสุดท้าย (ถ้าหารเหลือเศษ 11 ก็ ตอบ 1 เศษ 10 ก็ตอบ 0)

55 FILE Any of you have never worked with ﬁle? Since you are all have worked with it. You better know how to work with it correctly. None

56 FILE MODES IN PYTHON FILE Mode Description ‘r’ This is the default mode. It Opens file for reading. ‘w’ This Mode Opens file for writing. If file does not exist, it creates a new file. If file exists it truncates the file. ‘x’ Creates a new file. If file already exists, the operation fails. ‘a’ Open file in append mode. If file does not exist, it creates a new file. ’t’ This is the default mode. It opens in text mode. ‘b’ This opens in binary mode. ‘+’ This will open a file for reading and writing (updating)

57 EX01 OPEN AND READ A FILE FILE Python use concept of open and close file like we had in C, Java • 1) Open the file in Read mode with open() • 2) We use the mode function in the code to check that the file is in open mode. If yes, we proceed ahead • 3) Use f.read() or f.readline() to read file data and store it in variable content • 4) print contents

58 EX02 WRITE A FILE CONTENT FILE Python use concept of open and close file like we had in C, Java • 1) Open the file in Write/Append mode with open() • 2) Create some content and f.write(‘content inside’) • 3) Use f.close() to close the file (save) • 4) To Append, process is the same except open() with ‘a+'

59 EX03 READ / WRITE THE MODERN WAY FILE Python 3 can use ‘with’ block to read/write ﬁle # Writing to a file contents = {"aa": 12, "bb": 21} with open("myfile2.txt", "w+") as file: file.write(json.dumps(contents)) # writes an object to a file # Reading from a file with open('myfile1.txt', "r+") as file: contents = file.read() # reads a string from a file print(contents) # print: {"aa": 12, "bb": 21}

60 CSV FILE When we process something, data input or output may be any formats. CSV is one of the primitive data since the early age of computer. And it still very important in this Big Data Era.

61 EX01 READ CSVCSV Programming language Designed by Appeared Extension Python Guido van Rossum 1991 .py Java James Gosling 1995 .java C++ Bjarne Stroustrup 1983 .cpp • 1) import csv • 2) Open the ﬁle in ‘rt' mode with open() • 3) Use csv.reader() to read the ﬁle by Row • 4) Use csv.DictReader() to read each row, column as Dictionary

62 EX02 WRITE CSVCSV • 1) import csv • 2) Open the ﬁle in Write/Append mode with open() • 3) Use writer = csv.writer(ﬁle, delimiter=',', quotechar='"', quoting=csv.QUOTE_MINIMAL) • 4) writer.writerow(['Programming language', 'Designed by', 'Appeared', 'Extension'])

63 DATABASE While working with CSV is pretty easy. It’s still very basic in terms of relationship and connection between each other entities. Relational Database Management System (RMDB) and Structured Query Language (SQL) seems like the backbone of data management system. “No matter what it takes. Learn it, you must.” – Master Yoda

64 BASIC OF RELATIONAL DATABASE Deﬁnitions • Database • Table • Field (Column) • Record (Row) • Primary Key (PK) • Foreign Key (FK) • One to Many • Many to Many

65 SNIPPETS Learn How To Create Snippets To Save Your Time Of programmers don’t know How to Create Snippets. Is the time you may save writing code/ﬁx spelling/pull your hair by using Snippets. 90% 30%

66 SQL LANGUAGE WITH SQLITE import sqlite3 from sqlite3 import Error def create_connection(db_file): """ create a database connection to a SQLite database """ conn = None try: conn = sqlite3.connect(db_file) print(sqlite3.version) except Error as e: print(e) finally: if conn: conn.close()

67 SQL LANGUAGE WITH SQLITE (CONT) . . . . . conn = None try: conn = sqlite3.connect(db_ﬁle) print(sqlite3.version) except Error as e: print(e) ﬁnally: if conn: conn.close() if __name__ == '__main__': create_connection(r"C:sqlitedbpythonsqlite.db")

68 EX01 MANIPULATE TABLE -- tasks table -- sql_create_tasks_table = CREATE TABLE IF NOT EXISTS tasks ( id integer PRIMARY KEY, name text NOT NULL, priority integer, project_id integer NOT NULL, status_id integer NOT NULL, begin_date text NOT NULL, end_date text NOT NULL, FOREIGN KEY (project_id) REFERENCES projects (id) ); -- projects table -- sql_create_projects_table = CREATE TABLE IF NOT EXISTS projects ( id integer PRIMARY KEY, name text NOT NULL, begin_date text, end_date text );

69 EX01 MANIPULATE TABLE (CONT) def create_table(conn, create_table_sql): """ create a table from the create_table_sql statement :param conn: Connection object :param create_table_sql: a CREATE TABLE statement :return: """ try: c = conn.cursor() c.execute(create_table_sql) except Error as e: print(e)

70 EX01 MANIPULATE TABLE (CONT) def main(): database = r"C:sqlitedbpythonsqlite.db" sql_create_projects_table = """ CREATE TABLE IF NOT EXISTS projects ( sql_create_tasks_table = """CREATE TABLE IF NOT EXISTS tasks ( # create a database connection conn = create_connection(database) # create tables if conn is not None: # create projects table create_table(conn, sql_create_projects_table) # create tasks table create_table(conn, sql_create_tasks_table) else: print("Error! cannot create the database connection.")

71 EX02 SELECT DATA def select_all_tasks(conn): """ Query all rows in the tasks table :param conn: the Connection object :return: """ cur = conn.cursor() cur.execute("SELECT * FROM tasks") rows = cur.fetchall() for row in rows: print(row)

72 EX02 SELECT DATA (CONT) def select_task_by_priority(conn, priority): """ Query tasks by priority :param conn: the Connection object :param priority: :return: """ cur = conn.cursor() cur.execute("SELECT * FROM tasks WHERE priority=?", (priority,)) rows = cur.fetchall() for row in rows: print(row)

73 EX03 INSERT DATA def create_task(conn, task): """ Create a new task :param conn: :param task: :return: """ sql = ''' INSERT INTO tasks(name,priority,status_id,project_id,begin_date,end_date) VALUES(?,?,?,?,?,?) ''' cur = conn.cursor() cur.execute(sql, task) return cur.lastrowid

74 EX03 INSERT DATA (CONT) def main(): database = r"C:sqlitedbpythonsqlite.db" # create a database connection conn = create_connection(database) with conn: # create a new project project = ('Cool App with SQLite & Python', '2015-01-01', '2015-01-30'); project_id = create_project(conn, project) # tasks task_1 = ('Analyze the requirements of the app', 1, 1, project_id, '2015-01-01', '2015-01-02') task_2 = ('Conﬁrm with user about the top requirements', 1, 1, project_id, '2015-01-03', '2015-01-05') # create tasks create_task(conn, task_1) create_task(conn, task_2)

75 EX04 UPDATE DATA def update_task(conn, task): """ update priority, begin_date, and end date of a task :param conn: :param task: :return: project id """ sql = ''' UPDATE tasks SET priority = ? , begin_date = ? , end_date = ? WHERE id = ?''' cur = conn.cursor() cur.execute(sql, task) conn.commit()

76 EX04 UPDATE DATA (CONT) def main(): database = r"C:sqlitedbpythonsqlite.db" # create a database connection conn = create_connection(database) with conn: update_task(conn, (2, '2015-01-04', '2015-01-06', 2))

77 EX05 DELETE DATA def delete_task(conn, id): """ Delete a task by task id :param conn: Connection to the SQLite database :param id: id of the task :return: """ sql = 'DELETE FROM tasks WHERE id=?' cur = conn.cursor() cur.execute(sql, (id,)) conn.commit() def main(): database = r"C:sqlitedbpythonsqlite.db" # create a database connection conn = create_connection(database) with conn: delete_task(conn, 2); # delete_all_tasks(conn);

Well Grounded Python Coding - Revision 1 (Day 1 Slides)

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