Compare Python With Javascript

javascript, python

This note write some difference between JS with Python from a JS developer learning Python

comment in code

(*) nice tutorial resource: https://data-flair.training/blogs/python-tutorials-home/

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    // this is single line comment

    /**
     * this is block of comment
     */

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    # this is single line comment

    """
     " this is block of comment
    """
    """this is docstring in function use in function define"""

Data type

  • Javascript has 7 basic types in JavaScript:

    • number
    • string
    • boolean [true, false]
    • null
    • undefined
    • object
    • symbol

    refer: Javascript Info

  • Python has 5 standard Data Types:

    • Numbers

      • int………a = 10………..Signed Integer
      • long……..a = 345L………(L) Long integers, they can also be represented in octal and hexadecimal
      • float…….a = 45.67……..(.) Floating point real values
      • complex…..a = 3.14J……..(J) Contains integer in the range 0 to 255.
      • use conversion functions (int(), long(), float(), complex()) to convert data from one type to another
    • String

    • List

      • like array in js(ex: a = [1, 2 , 3])

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        mylist = ['Rhino', 'Grasshopper', 'Flamingo', 'Bongo']
        B = len(mylist) # This will return the length of the list which is 3. The index is 0, 1, 2, 3.
        print mylist[1] # This will return the value at index 1, which is 'Grasshopper'
        print mylist[0:2] # This will return the first 3 elements in the list.

      • dynamic and mutable

    • Tuple
      • like list but use parenthesis () instead of square bracket [] (ex: a = (1, 2 , 3))
      • fixed size and immutable

    • Set

      • like list but use curly braces {} instead of square bracket [] (ex: a = {1, 2 , 3})
      • dynamic, mutable and unique value
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        lst = [1,2,2,3] # 1 list with duplicated with `2`
        st = set(lst)
        #or
        st = {1,2,2,3} 
        print st # -> set([1, 2, 3])

    • Dictionary

      • like json in js 
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        room_num = {'john': 425, 'tom': 212}
        room_num['john'] = 645  # set the value associated with the 'john' key to 645
        print (room_num['tom']) # print the value of the 'tom' key.
        room_num['isaac'] = 345 # Add a new key 'isaac' with the associated value
        print (room_num.keys()) # print out a list of keys in the dictionary
        print ('isaac' in room_num) # test to see if 'issac' is in the dictionary.  This returns true.

    refer: rhino3d

    variable

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      let a = 1
      const b = 2
      var c = 3

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      a = 1
      b = 2

      a, b, c = 1, 2, 3

      a, b, c = 4
      ...

condition

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    if(a){

    } else if(b){

    } else {

    }

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    if a:

    elif b:

    else:

operator

Javascript Operator

Python Operator

ternary operator

  • js

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    const a = b > 10 ? 10 : b

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    #1. basic:
    syntax: [on_true] if [expression] else [on_false]
    a = 10 if b > 10 else b
    #2. use tuple
    syntax: [tuple][condition]
    a,b = 1,2
    c = (a,b)[a>b]
    #3. use Dictionnaries
    {False:f"b:{b}",True:f"a:{a}"}[a>b]
    #4. use lambda
    (lambda :f"b:{b}",lambda :f"a:{a}")[a>b]() # sooooooo complex

refer: data-flair

loop

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    for(let i = 0; i < 10; i++){
      
    }
    for(let i in array){//i : index

    }
    for(let v of array){ // v : value
    }
    ...
  • py
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    for i in arr:

code block

  • js use {}

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    if ( a > b ) {
      alert(a)//use new line character..
    } else {
      alert(b); // ..or `;` to end line
    }

  • py: use space

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       if a > b: 
          print a # use new line character
        else:
          print b
      
        # if want prevent new line break line use \ character like belove
        sum = 1 + 3 + 5 + \
          7 + 9 + 11 + \
          13 + 15 + 17
        
        #or
        message = """This is a string that will span across multiple lines. Using newline characters
    and no spaces for the next lines. The end of lines within this string also count as a newline when printed"""

    use space & new line to break

function

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    function a(){}
    const a = function () {
      alert('anph');
    }
    const b = function () {
      alert('anph');
    }

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    def a():
      print 'anph'

    arrow | lambda

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    const sum = (a, b) => a + b

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    sum = lambda a, b: a + b

switch case

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    switch(x){
      case 1:
      break;
      case 2:
      break;
      case 3:
      break;
      ...
      default:
      break;
    }

  • py: python éo có, vâng python éo có switch case và phải tự chế -_-

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    #1. kiểu truyền thống: use dictionary
      def week(i):
      switcher={0:'Sunday',1:'Monday',2:'Tuesday',3:'Wednesday',4:'Thursday',5:'Friday',6:'Saturday'}
      return switcher.get(i,"Invalid day of week")
    #########
    >>> week(2)
    'Tuesday'
    >>> week(0)
    'Sunday'
    >>> week(7)
    'Invalid day of week'
    >>> week(4.5)
    'Invalid day of week'


    #2. Using Python Functions & Lambdas
    def zero():
      return 'zero'
    def one():
      return 'one'
    def indirect(i):
      switcher = { 0:zero, 1:one, 2:lambda:'two' }
      func = switcher.get(i,lambda :’Invalid’)
      return func()
    >>> indirect(4)
    ‘Invalid’
    >>> indirect(2)
    'two'
    >>> indirect(1)
    'one'
    >>> indirect(0.5)
    'Invalid'


    #3. With Python Classes
    class Switcher(object):
      def indirect(self,i):
        method_name='number_'+str(i)
        method=getattr(self,method_name,lambda :'Invalid')
        return method()
    def number_0(self):
      return 'zero'
    def number_1(self):
      return 'one'
    def number_2(self):
      return 'two'
    ##
    >>> s=Switcher()
    >>> s.indirect(2)
    'two'
    >>> s.indirect(4)
    'Invalid'
    >>> s.number_1()
    'one'
    `

map()

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    const numbers = [1,2,3,4,5,6,6,7,8,9,0]
    const map0 = numbers.map(x=>x*2)
    //->[2, 4, 6, 8, 10, 12, 12, 14, 16, 18, 0]

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    numbers = [1,2,3,4,5,6,6,7,8,9,0]
    map0 = list(map(lambda x:x*2, numbers))
    #->[2, 4, 6, 8, 10, 12, 12, 14, 16, 18, 0]

filter()

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    const numbers = [1,2,3,4,5,6,6,7,8,9,0]
    const filter0 = numbers.filter(x=>0===x%2)
    //->[2, 4, 6, 6, 8, 0]

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    numbers = [1,2,3,4,5,6,6,7,8,9,0]
    map0 = list(map(lambda x:x*2, numbers))
    #->[2, 4, 6, 8, 10, 12, 12, 14, 16, 18, 0]

reduce()

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    const numbers = [1,2,3,4,5,6,6,7,8,9,0]
    const reduce0 = numbers.reduce((a,b)=>a+b)
    //->51

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    #map
    numbers = [1,2,3,4,5,6,6,7,8,9,0]
    reduce0 = reduce(lambda a,b: a+b, number)
    #->51

exception

  • throw | raise

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      function a(e){
        if(e) throw 'e'
      }

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      def a(e):
        if e
          raise Exception

  • try catch | try except

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      try{

      }catch(e){
        console.log(e)
      }

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      try:

      except:
        print sys.exc_info()[0]

a bit bonus

Feature Javascript Python desc
repeat string ‘str'.repeat(10) 'str' * 10 o_0
power number Math.pow(2, 3) 2 ** 3 amazing
sum array [1,2,3] + [4,5,6] => 1,2,34,5,6 [1,2,3] + [4,5,6] => [1, 2, 3, 4, 5, 6] amazing

OOP

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    /**
     * Đây là docstring. Một lớp mới vừa được khai báo.
     */
      class Anph extends ClassParent {//single extend
        constructor(){

        }
        //more code
      }
      //use
      const anph = new Anph()

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     class Anph(ClassParent, ClassParent2):# multi-extends able
      '''Đây là docstring. Một lớp mới vừa được khai báo.'''
      def __init__():
        
      #more code

    #use
    anph = Anph()