Python 101! Introduction to Python

print('Hello, World!')

Python3 app.py

Hello, World!

# single line comment'''multiline commentUsing  docstring'''

print(46 + 2)  # 48 (addition)print(10 - 9)  # 1 (subtraction)print(3 * 3)  # 9 (multiplication)print(84 / 2)  # 42.0 (division)print(2 ** 8)  # 256 (exponent)print(11 % 2)  # 1 (remainder of the division)print(11 // 2)  # 5 (floor division)

favourite_food = "Rsti"print(favourite_food)

favourite_food = "Rsti"print(favourite_food)favourite_food = 26print(favourite_food)favourite_food = Falseprint(favourite_food)

# logical operators:laundry_day = "Monday"today = "Tuesday"on_vacation = Falseif today is laundry_day and today is not "Sunday" and on_vacation is False:  print("It's laundry day!")else:  print("The laundry can wait!")# comparison operators:age = 21if age >= 21:  print("You can drive a trailer")elif age >= 16:  print("You can drive a car")else:  print("You can ride a bike")  

#Example 1:language = "Python"#Example 2:multiline_str = '''oneperline'''  #Example 3, escape characters:escape_str = "She said: \"Python is great!\""print(escape_str) # She said: "Python is great!"  # Example 4, concatenate strings:one = "Lux"two = "Academy"print(one + " " + two) # Lux Academy # Example 5: interpolation.# method 1first_name = "Lux"last_name = "Academy"greet = f"Welcome at {first_name} {last_name}!" print(greet)  # Welcome at Lux Tech Academy!# method 2first_name = "Lux"last_name = "Academy"greet = 'Welcome at {} {}!'.format(first_name, last_name)print(greet)  # Welcome at Lux Tech Academy!# method 3first_name = "Lux"last_name = "Academy"greet = 'Welcome at{first} {last} !'.format( first=first_name, last=last_name) print(greet)  # Welcome at Lux Tech Academy!#Example 6, extract substringsname = "Monty Python"print(name[6:9]) # Pytprint(name[6:]) # Pythonprint(name[:5]) # Monty

age = 18 # intpi = 3.14 # floattotal = age + pi # floatprint(type(age), type(pi), type(total)) # <class 'int'> <class 'float'> <class 'float'>

# booleansa = Trueb = Falseif a is True and b is False:  print("YAY!")

# can store any data typemultiple_types = [True, 3.7, "Python"]# access and modifyfavourite_foods = ["pasta", "pizza", "french fries"]print(favourite_foods[1]) # pizzafavourite_foods[0] = "rsti"print(favourite_foods[0]) # rsti# subsetsprint(favourite_foods[1:3]) # ['pizza', 'french fries']print(favourite_foods[2:]) # ['french fries']print(favourite_foods[0:2]) # ['rsti', 'pizza']# appendfavourite_foods.append("paella")# insert at indexfavourite_foods.insert(1, "soup")# removefavourite_foods.remove("soup")# get lengthprint(len(favourite_foods)) # 4# get subset (the original list is not modified)print(favourite_foods[1:3]) # ['pizza', 'french fries']# lists inside listsfavourite_drinks = ["water", "wine", "juice"]favourites = [favourite_foods, favourite_drinks]print(favourites[1][2]) # juice

#tuplesnew_tuple = ("a", "b", "c", "d")print(len(new_tuple)) # 4print(new_tuple[1]) # bprint(new_tuple[1:4]) # ('b', 'c', 'd')

language_creators = {  "Python" : "Guido van Rossum",  "C" : "Dennis Ritchie",  "Java" : "James Gosling",  "Go": "Robert Griesemer",  "Perl" : "Larry Wall"}# access, modify, deleteprint(language_creators["Python"]) # Guido van Rossumlanguage_creators["Go"] = ["Robert Griesemer", "Rob Pike", "Ken Thompson"]print(language_creators["Go"]) # ['Robert Griesemer', 'Rob Pike', 'Ken Thompson']print(len(language_creators)) # 5del language_creators["Perl"]print(len(language_creators)) # 4# print keys and valuesprint(language_creators.keys())print(language_creators.values())

# foor loopfor x in range(0, 3):  print(x)# loop through listfor x in ["Python", "Go", "Java"]:  print(x)# loop through dictionarylanguage_creators = {  "Python" : "Guido van Rossum",  "C" : "Dennis Ritchie",  "Java" : "James Gosling",}for key, value in language_creators.items():  print("Language: {}; Creator: {}".format(key, value))

# while looplevel = 0while(level < 10):  level += 1

# functionsdef allowed_to_drive(age):  if age >= 21:    return True  else:    return Falseprint(allowed_to_drive(42)) # Trueprint(allowed_to_drive(12)) # False

def is_laundry_day(today, laundry_day = "Monday", on_vacation = False):  if today is laundry_day and today is not "Sunday" and on_vacation is False:    return True  else:    return Falseprint(is_laundry_day("Tuesday")) # Falseprint(is_laundry_day("Tuesday", "Tuesday")) # Trueprint(is_laundry_day("Friday", "Friday", True)) # False

# classesclass Email:  # __ means private  __read = False  def __init__(self, subject, body):    self.subject = subject    self.body = body  def mark_as_read(self):    self.__read = True  def is_read(self):    return self.__read  def is_spam(self):    return "you won 1 million" in self.subjecte = Email("Check this out", "There are a bunch of free online course here: https://course.online")print(e.is_spam()) # Falseprint(e.mark_as_read())print(e.is_read()) # True

# inheritanceclass EmailWithAttachment(Email):  def __init__(self, subject, body, attachment):    super(EmailWithAttachment, self).__init__(subject, body)    self.__attachment = attachment  def get_attachment_size(self):    return len(self.__attachment)email_with_attachment = EmailWithAttachment("you won 1 million dollars", "open attachment to win", "one million.pdf")print(email_with_attachment.is_spam()) # Trueprint(email_with_attachment.get_attachment_size()) # 15

# writetodos_file = open("todos.txt", "wb")todos_file.write(bytes("buy a new domain name
", "UTF-8"))todos_file.write(bytes("work on the side project
", "UTF-8"))todos_file.write(bytes("learn a new programming language
", "UTF-8"))todos_file.close()# readtodos_file = open("todos.txt", "r+")todos_file_contents = todos_file.read()print(todos_file_contents)