README.md

python-ruby

• This repository is for learning both programming languages, python and ruby (parallel learning).

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How to run files for each in terminal

• go to terminal(cmd) - type -> python(ruby) "filelocation\filename.py(rb)"
  • if there is a space in the file location, use quotes

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Numeric expression

• arithmetic operator

python

• +, -, *, /
• use print fuction
• int / float / complex

ruby

• +, -, *, /
• use print fuction
• use puts function for a line-break

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More calculation

python

• import math module for calculation
  • round up a: math.ceil(a)
  • round down a: math.floor(a)
  • a to the nth power: math.pow(a,n)
  • pi value: math.pi

ruby

• round up a: a.ceil()
• round down a: a.floor()
• a to the nth power: a**n
• pi value: Math::PI
  • Be careful of capitalization

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String

python

• use print()

using quotes

• quotes "" or ''
• should be consistent
• if you want to express quotes inside the string, use a different quote from the quotes used for the string

using operators

• you can combine each string using +
• you can print a string several times using *
• 'string'[n] will print the (n-1)th letter in the string

editing strings

• 'string'.capitalize() - capitalize the first letter of the string
• 'string'.upper - capitalize the whole string
• 'string'.len or len('string') - print the length of the string by number
• 'string'.replace('stringa','stringb') - replace 'stringa' inside the string with 'stringb'

special characters

• : escape the role of the following sign, \ can also escape the role of \ itself
• \n: create new line within the string
• \t: create tab within the string
• \a: alert
• " and ' have the same role

operator +

• • is arithmetic operator between numbers
• • is concatenation operator between strings

ruby

using quotes, operators

• same syntax as python

editing strings

• 'string'.capitalize() - capitalize the first letter of the string
• 'string'.upcase() - capitalize the whole string
• 'string'.length() - print the length of the string by number
• 'string'.sub('stringa','stringb') - replace 'stringa' inside the string with 'stringb'

special characters

• , \n, \t, \a: same as python
• " and ' have slightly different role

operator +

• same as python

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Variable

python

basic grammar

• how to declare variable: variablename = data
• python automatically sets the data type of the variable based on the assigned data

string variable

• variablename = "myname"
• use "," or "+" to concatenate
  • "," makes an extra space

calculation

• variablename = number
• set equation using variable name

ruby

basic grammar

• same as python

string variable

• same as python
  • "," makes a linebreak
  • "+" makes an extra space

calculation

• same as python
  • gets: input() in python
  • to_i: change string into integer

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Comparison_boolean

python

• boolean: True / False
• ==,>,<

ruby

• boolean: true / false

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Conditional statements

python

• if True: - execute what comes after
• if False: - do not execute anything
• codes to be executed in conditional statements have indent
• can use comparison operator to make conditions
• else - can combine conditional statements that are closely related (True/False inverse), in order to make codes more concise
• else if - elif, reduce the length of the code, improve legibility and relationship between the codes

ruby

• if true - (without colon) execute what comes after
• if false - do not execute anything
• end - end the conditional statement
• not necessary, but can also make indent for legibility of the code
• can use comparison operator to make conditions
• else - same as python
• else if - elsif

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Input-Output

python

• input() - get external value
  • can have data inside () ex) input("please enter.")
• .upper - capitalize
• try not to name variable that is already in Python ex) input()
• match the data type when getting input

ruby

• gets.chomp() - input in python
• .upcase - capitalize

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Logical Operator

• And/Or/Not

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Comment

python

• #: does not execute the following line
  • can be used as a comment for readers of the code
• ''': does not execute the lines between ```, not recommended
  • means to express several lines of a string

ruby

• same as python
  • =begin ~ =end: works like ''' in python, but not recommended as well

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Container

python

• List: a container in python that can store multiple data
  • can store different data type in one list
  • index: the number of position of an element in a list
  • listname[i]: shows the element according to the list
    • listname[i] = newelement: replace the existing element at i with newelement
• type(A): shows the data type of A

ruby

• Array: same as a list in python
• A.class: shows the data type of A

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Function

• Function: modules of code that accomplish a specific task
  • can be used over and over again

python

• Create a function

def function_name()
    # content of the function
    # lines of codes
# return ~

• Implement the function

function_name()

ruby

• Create a function

def function_name()
    # content of the function
    # return ~
end

• Implement the function
  • same as python
• 2.rb file has several different ways of creating and implementing fuctions

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Block

ruby

• code block: Following some specific functions like times, upto, a code block is repeatedly executed.
• more effective code than a typical loop using while

5.times(){|i| puts i}

• each(): For each element in the array, repeatedly execute the code in the following block
  • more intuitive than loop
• delete_if(): Delete elements in the array according to the conditional statements in the code block
  • Use brackets if the code ends in one line, and do-end if it comes across multiple lines

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Module

• Module: a file containing codes to be imported to another program
• Without modules, programs with long codes will lead to a name conflict problem
• Modules can eliminate any duplication problem of using the same function placed in the different files, and increase recyclability of the function

python

• built-in module: python standard library
  • The library contains built-in modules (written in C) that provide access to system functionality such as file I/O that would otherwise be inaccessible to Python programmers, as well as modules written in Python that provide standardized solutions for many problems that occur in everyday programming python documentation
    • example: math

    import math
    math.ceil(2.1)

• from filename(module) import function: import the function from module to another file to use

from egoing import a
print(a())

• import filename(module): import every function in the module
  • need to indicate the module before the function

import egoing
print(egoing.a())

• import filename(module) as x: For convenience, use a different name(x) from the actual name of the imported module or the function when using it

import egoing as k
print(k.a())

ruby

• built-in module example: Math

Math.sqrt(16)

• how to create a module
  • declare module name: module Module_name ~ end
    • fist alphabet of the module name is capitalized
  • make function within the mudule module's function: module_function()

module Egoing
    module_function()
    def a()
        return 'a'
    end
end

• how to import module from a different file
  • require('Module_name') or require 'Module_name'
    • error due to the directory
  • require(./'Module_name')
    • .: current directory
      • find the module from the directory of the file to execute
      • editor error due to directory
  • require_relative './Module_name'
    • relative: execute the file in the same directory

require 'Egoing'
require './Egoing'
require_relative './Egoing'
puts(Egoing.a())

Object Oriented Programming

• use an object to create a better code

python

ruby