PythonForDataScience.txt

Python Data Types
==================
int - 666666
float - 123.123
str - "Hello Python 101"
bool - True, False
type(11) - result will be datatype
data type casting - int('1'), int(1.0), float('1.1'), str(1.1), str(1), int(True),bool(1) 

Python Expression and Variables
================================
mathematical operations
10+20 (10,20 operands, + operator)
+
-
*
/ - result default float value
// -  result int value
() - first priority
*, / - highest priority
+, - - second priority
variables - To store values (my_var=1)
last value will be overide in the variable

String Operations
==================
single quotes/double quotes for string representaion
Name [::2]: print the odd number 0,2,4,6.....
Name [0:5:2]: print odd number 0,2 (from first  character)
Name [8:12]: print the character from 8th index to 11th index(11+1)
len() - find the length of the string
+ - to concatinate the string
* - to replicate the string multiple times (3 * "Hello")
Name.find('el'): print the first index
Name.replace('apple','pineapple')
Name.upper

Python Data Structures
=======================
Lists and Tuples
*****************
Lists and Tuples are Compound data types
Ordered sequence
Ratings=(10.9,6,5,10,8,9,6,2)
comma separated values within paranthesis
tuple1=('masco',10, 1.2,True)
tuple3[0:3]
len(tuple3)
Tuples are immutable
sorted(tubles3) - functions
Tuples support nested tuples

Lists
*****
lists are represented with square bracket
lists are mutable
all data types are allowed inside the list
it supports nested list
python supports negative index
lists and tuples are identical except immutable
using extend() method we can change the existing list
convert string to list using split function


Sets
*****
It is unordered and not maintain any position
having unique elements - remove duplicates
exset={"summer","monsoon","autumn","winter","spring","summer"}
convert list to set use function set(list)
in operator to check the contenet
"A" in albumset - return True,False
& used to union 2 sets - only intersection/common value
union function will merge 2 sets

Dictionaries
*************
Key value pairs
{"key1":value1,"key2":value2,"key3":value3}
DICTNAME["key"]
del(DICTNAME["key"])
in function to check the key availabilty - "key" in DICTNAME
DICTNAME.keys() - return all keys
DICTNAME.values - return all values

Python Programming Fundamentals
================================
Conditions and Branching
*************************
comparision operator
==,>=,<=,>,<,!=
if(a>b):
else:
elif(a==b):
logic operator: not(True),not(False), if(a>10) or (b<50), and

Loops
******
range(3) -> [0,1,2] sequnce of numbers python2 output, range(0,3) in python3 output
range(10,15) -> [10,11,12,13,14]
for i in range (0,5):
for square in squares:
for i,square in enumerate(squares):
while loops

Functions
**********
python builtin functions - len, sum, sorted
Documentation string """ add 1 to a """
collecting arguments def collection(*names)
global scope - variable can be accessed in anywhere 
local scope - scope within function during execution post that variable will be deleted
if local variable not available then the global variable value will be taken for function execution
you can define local variable as global scope with global <variable> key name

Objects And Classes
********************
python each is an object
class Circle(object): here object is a parent class
__init__ python class constructor
dir(objectname) - print all attributes

To install matplotlib
@@@@@@@@@@@@@@@@@@@@@@
I had to install libxft-dev in order to enable matplotlib on ubuntu server
sudo apt-get install libfreetype6-dev libxft-dev
sudo easy_install matplotlib
sudo easy_install pandas
sudo easy_install numpy
sudo pip install xlrd

Working with Data in Python
============================
File1=open("/resources/file1.txt","r")
mode - r (read), w (write), a (append)
read() - read the whole file
readlines() - return the list
readline() - return only one line
readlines(16) - print 16 character, readlines(5) print next 5 character

pandas - popular library for data analysis
df.head() - print first 5 record
read_csv() - read the csv file
read_excel() - read the excel file
read_fwf() - read the text file
 
actor_name=df3[['Name']]
name_rating=df3[['Name','Rating']]
df3.ix[0,0]
df3.ix[0,'Rating']
df3.ix[0:2,0:3]
df3.ix[0:2,'Name':'Rating']
unique() - print the unique value after removing duplicate

Working with Numpy Arrays
==========================
Numpy 1D Array
***************
It is array and fixed size. Array having similar datatype
list1=[0,1,2,3,4,5,6,7,8]
import numpy as np
a=np.array(list1)
a.size
a.ndim
a.shape
b=a[1:4] - ouput [1,2,3]
list1=[0,1,2,3,4,5,6,7,8]
index= 0 1 2 3 4 5 6 7 8
length=1 2 3 4 5 6 7 8 9
a[3:5]=300,500

numpy basic operations
    vector addition and substraction
    u=[1,5],v=[4,1] z=u+v=[5,6]
    u-v
    u*2
    product of two numpy arrays
    u dot v        T
    dot product - u v - 1*4+5*1=9
    np.dot(u,v)
    Broadcasting - u+1 - adding 1 with each element in numpy array
    universal Functions
    --------------------
    a.mean()
    a.max()
    sin()
    np.linspace(-2,2,num=5) - -2,-1,0,1,2 (total 5 values)
    
    Numpy 2D Arrays
    ----------------
    a=[[11,12,13],[21,22,23],[31,32,33]]
    np.array(a)