Learn Python - Basics

It is very excited to learn python (I recommend to use python3 directly which will have better support in the future). First, let’s start with an IDE.

Here are three IDEs I like very much.

• IDLE, it is installed along with the Python installer, which provides a powerful shell of playing with python.
• PyCharm, JetBrains provides the most powerful IDE for python, it supports many useful functions like refactoring, lint and so on.
• VSCode is a lightweight IDE for python as well, but you need to install some plugins to support python better. Here are plugins recommended.
  • Code Runner for executing python
  • Python support code intellisence, code formatting, auto indent etc.
  • Pylint is recommended as well.

Here are some points for python, I will make it simple as possible.

• Number

  number = 51
  print(number)
  
  number = 51.3
  print(number)
  
  number1 = number / 2
  print(number1)
  
  number2 = number // 2
  print(number2)

• String

  str = "Hello World"
  print(str)
  
  str1 = 'Hello World'
  print(str1)
  print(str1[0:2])
  print(str1[:6])
  print(str1[6:])
  print(str1.upper())
  print(len(str1))
  
  # if we have some ESC, 'r' means 'raw'
  str1 = r'Hello \r\n Howard!'
  print(str1)

• List

  ls = [1, 2, 3, 4, 5]
  print(len(ls))
  
  ls.append(6)
  print(ls)
  
  ls1 = ls + [7, 8]
  print(ls1)
  
  ls2 = ls1[:2]
  print(ls2)
  
  ls3 = range(0, 10)
  for i in ls3: print(i)
  
  ls3 = range(2, 10)
  for i in ls3: print(i)
  
  ls3 = range(0, 16, 4)
  for i in ls3: print(i)

• if: elif: else (note: is and == are both fine to check the equalvity)

  s = 's'
  if(s == 'a'): print('alpha')
  elif(s is 'b'): print('beta')
  elif(s is 's'): print('superman')
  else: print('unknown')

• for loop

  items = [1, 4, 2, 6, 9, 7]
  for i in items: 
      print(i)
  
  for i in items[:4]:
      print(i)

• while loop (note: while, is, break, continue)

  i = 0
  while i < 10:
      print(i)
      i += 1
      if i is 5: break
      else: continue

• Comments (single-line and multi-line)

  # num = 20
  
  """
  str = 'hello'
  str += ' world'
  print(str)
  """

• Function

  # void
  def say_hello(name): 
      print('Hello', name)
  
  say_hello('Howard')
  
  # with return value
  def get_hello_message(name):
      return 'Hello ' + name
  
  print(get_hello_message('Howard'))
  
  # with default value
  def say_hello_with_default_value(name = 'Howard'):
      print('Hello', name)
  say_hello_with_default_value()
  say_hello_with_default_value('Bibioo')
  
  # with optional parameters
  def someone_do_something(name = 'Howard', action = 'ate', something = 'an apple'):
      print(name, action, something)
  
  someone_do_something()
  someone_do_something('Bibioo', 'is', 'awesome')
  someone_do_something(something = 'us', action = 'blesses', name = 'God')
  
  # flexibale variables
  def flexible_var(*args):
      print('it has', len(args), 'arguments')
      for i in args:
          print(i)
  flexible_var('a', 'b', 'c')
  
  # unpack aruments, watch out the compare of the last two calls
  def unpack_arguments(age, apple_pw, smook_pw):
      health = (100 - age) + (apple_pw * 3.5) - (smook_pw * 4.5)
      print(health)
  
  person_data = [35, 7, 0]
  unpack_arguments(person_data[0], person_data[1], person_data[2])
  unpack_arguments(*person_data)

• Set

  my_shopping_cart = {'apple', 'milk', 'beer', 'milk'}
  print(my_shopping_cart)
  print(len(my_shopping_cart))
  print('milk' in my_shopping_cart)

• Dictionary (watch out the three different loops)

  classmates = { 'Tony': 'cool but smells', 'Emma': 'sits behind me', 'Lucy': 'asks me too much questions' }
  print(len(classmates))
  print(classmates['Tony'])
  for i in classmates:
      print(i)
  for i in classmates.items():
      print(i)
  for k, v in classmates.items():
      print(k, v)

Now here are the basics for Python to remember, get back if need to recall the points, I will do more excited thing in the next part.