PYTHON BASICS SIMPLIFIED

PYTHON BASICS SIMPLIFIED

What is Python?

Python is a high level multipurpose scripting language used in web development, desktop application development, artificial intelligence, machine learning, game development, automation, tools development and a lot more.

Why Python?

  •  Easy Syntax & Readability
  •  Extensive standard library
  •  Large community
  •  Object oriented like any other efficient programming language.
  •  Many popular companies like Youtube, Instagram, 
 Pinterest etc., use Python.

Getting Started

Installation: 

             Instructions available at

Getting familiar with basic syntax:

  • Check basic python information on your machine such as python version using the command “python”. 
  • Standard output: Use the command “print” to print data to output. (use command “print()” from python3)
  • Identifiers (Variables, Functions, Classes, Modules etc.,): Can be alphanumeric and are case-sensitive.
  • Comments starts with  a ‘#’ symbol.

             Example: #This is a comment
  • Multi-line comments can be placed in between 3 quotes.
      
    Example:
    ‘’’This is a
                    
    multiline comment
                    
    !’    ’’
  • Strong Indentation: 
Python will not use braces to define blocks like other object oriented languages.
 So, it enforces very strict indentation to define blocks.
             Example: 
                
             def func(a):
                     
                  return a

    TIP: Xcode for osX and PyScripter for windows are the simplest IDEs to begin with. 
        
            To practice stra    ight away, logon to https://repl.it/languages/python

 Python Variables

Below given are the python variable types.
  • Number : (Int, Long, Float, Complex)
  • String: ‘’ or “ ” or “”” “””
  • Tuple(): Allows all types of data types which applies to Lists too. Read only data type.
  • List[]: List comprehension is one of the most useful concepts in Python along with Lambda expressions, RegEx
  • Dictionary{}: unordered Key-value pairs.
  • Type casting is done using the data type.
  • Useful operators like floor division (//), exponent (**), IN and NOT IN, IS and IS NOT are available along with all other basic operators.

Conditionals and Loops

  • Conditionals:
    • If
    • If..Else
    • Nested If
  • Loops: List Comprehension comes handy with loops
    • For
    • While
    • Nested loops 

 Useful Functions

  • Number Functions:
            abs(a), ceil(a), exp(a), max(), min(), pow(a,b), sqrt(a), round(a,n)
  • String Functions:
            find(string,x,y), upper(), lower(), isdigit(), isalpha(), replace(x,y,count), min(), max(),        
            capitalize(), count(x,S,E)
  • List Functions:
            len(list), list.sort(), list.insert(pos,val), list.remove(val), list.count(obj), cmp(X1,X2), min(),
            max()
  • Tuple Functions:
             len(tuple), cmp(X1,X2), min(), max()
  • Dictionary Functions:
            Del d[‘key’], d.clear(), del d, d.keys(), d.values(), d.items(), cmp(d1,d2), len(d),
            d.has_key(key)

DateTime


Python has great libraries like “time”, “datetime”.

  • Below code outputs a ‘structure’ as shown in the result

    
    Import time
     
    print(time.localtime(time.time()) 



    #result:
    time.struct_time(tm_year=2017, tm_mon=10, tm_mday=10, tm_hour=10, tm_min=43, tm_sec=3, tm_wday=1, tm_yday=283, tm_isdst=0)
  • You can get a better format as below.

    time.asctime(time.localtime(time.time()))
    # -> Tue Oct 10 10:48:33 2017
  • Breaking up time attributes:


    import datetime
    
now = datetime.datetime.now()

    print now.year, now.month, now.day, now.hour, now.minute, now.second

    Result: 2017 10 10 10 57 38

Calendar

The “calendar” module helps to import calendar into our program. Given below is an example.

 import calendar

x = calendar.month(2017, 10)

print x



Printing calendar for complete year: x = calendar.calendar(2017)
Finding leap year: print calendar.isleap(2017)
Finding the weekday (0 to 6): print calendar.weekday(2017,10,22)

Functions

The best illustration of code reusability. Below shown is the syntax.

 def functionname(arg1,arg2,….):
       
         <logic>
       
return [expression] #optional

functionname(arg1,arg2,….) #arguments can be a value or a reference

 Example:

 print "Even number generator"

limit=input("Enter the upper limit:")

even_list=[]


 def eve(x):
 
    for i in range(0,x):
  
          if i%2==0:
    
            even_list.append(i)

    return even_list

print eve(limit)

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