Chapter 4 Numbers

Chapter 4 Numbers Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012

Python Build-in types • Numbers 3.1415 • Strings “Hello World” • Lists [1,2,3,4] • Files input=open(‘file.txt’, ‘r’)

Numbers Many different types, we only provide 3 here for now: • Integer • Floating-point • Long integer

Number in Action • Perhaps the best way to understand numerical objects is to see them in action. >>> a=3 #Name Created >>> b=4

Number in Action >>> a+1 # (3+1) 4 >>> a-1 #(3-1) 2

Number in Action >>> b*3 12 >>>b/2 2

Number in Action >>> b**2 #power 16 >>> a%2 #remainder 1

Number in Action >>> 2+4.0, #mix type 6.0 >>> 2.0**b 16.0

Number in Action >>> b / 2 + a >>> b/(2.0+a) >>> b/(2+a)

Number in Action >>> 1 / 2.0 0.5 >>> 1/2 0

Long Integers >>> 2L ** 200 >>> 2 ** 200

Class Practice >>> num= 1/3.0 >>> num >>> 2L*200 >>> a=10 >>> b=20 >>> c=a+b >>> c

Other Numeric Tools >>>int(2.567) 2 >>> round(2.567) 3.0 >>> round(2.567, 2) 2.57

Other Numeric Tools Math library >>> import math >>> math.pi 3.141592653589793 >>> math.e 2.718281828459045 http://docs.python.org/library/math.html

Other Numeric Tools • Random Library >>> import random >>> random.randint(1,100) 25 >>> random.randint(1,100) 45 >>> random.randint(1,100) 17 http://docs.python.org/library/random.html

Dynamic Typing >>> a = 3 • Create an object to represent the value of 3 • Create the variable a, if it does not yet exist • Link the variable a to the new object 3

a = 3

Share Reference >>> a=3 >>> b=a

Share Reference >>>a=3 >>>b=a >>>a=5

Dynamic Typing >>>a=3 >>>b=a >>>a=5.0

Class Practice >>> int(3.1415926) >>> round(3.1415926) >>> round(3.1415926, 3) >>> import math >>> round(math.pi, 3)

Class Practice >>> a=10 >>> b=20 >>> a+b >>> a=a+10 >>> a >>> b=b+10.0+a >>> b

Chapter 4 Numbers