Python Intrinsic Data Type

Overview

Python has these common built-in Data Types: https://docs.python.org/2/library/stdtypes.html

Numeric
String
Boolean
List
Tuple
Dictionary
Set

Python will set the variable type once it is assigned. You can change the variable type if the new variable value is set to another type. For example:



In [3]:

    
var = 321 # Create an integer assignment.
print type(var)
var = 'HKU' # The new `var` variable is now become a string type.
print type(var)









    



<type 'int'>
<type 'str'>

Numeric

Numeric Types are basic data storage in nearly every programming languages. In python, they can be : int, long, float and complex.

Type	Format	Description
int	`a = 10`	Signed Integer
long	`a = 345L`	(L) Long integers
float	`a = 45.67`	(.) Floating point real values
complex	`a = 3.14j`	(j) Complex number, Python use `j` to denote the imaginary part.

Python numbers variables are created by the standard assign method:



In [20]:

    
a = 68
print a,"is a",type(a)

b = 32385848583853453453255459395439L
print b,"is a",type(b)

c = 45.67
print c,"is a",type(c)

d = 3.14j
print d,"is a",type(d)









    



68 is a <type 'int'>
32385848583853453453255459395439 is a <type 'long'>
45.67 is a <type 'float'>
3.14j is a <type 'complex'>

Arithematic

Basic arithmatic functions You can print different variables at the same time with comma-separated, and the different arthimatic operations are showned



In [29]:

    
a = 10
b = 15
print a + b , a - b , a * b , a / b









    



25 -5 150 0

String

String types are created by enclosing characters in quotes. Single quotes ' double quotes " can be used to denote a string in one-line. The triple quotes """ can define a multi-line string. They shall be in pairs.



In [26]:

    
Name = 'Stephen Ng'
Subject = "Lunar eclipse open house today"
Email = "ncy@astro.physics.hku.hk"
Content='''There will be a lunar eclipse observable in Hong Kong on Jan 31 starting at 19:48pm. The Department will arrange an open house for the observatory at the roof from 7pm.
'''



In [28]:

    
print "from:", Name, '<'+Email+'>'
print "subject:", Subject
print "-------------------------------------------"
print Content









    



from: Stephen Ng <ncy@astro.physics.hku.hk>
subject: Lunar eclipse open house today
-------------------------------------------
There will be a lunar eclipse observable in Hong Kong on Jan 31 starting at 19:48pm. The Department will arrange an open house for the observatory at the roof from 7pm.



In [30]:

    
print Content[0] # this will print the first character
print Content[1:5] # this will print the substring









    



T
here

Boolean



In [31]:

    
b1 = True
b2 = False
b3 = (b1 and b2) or (b1 or b2)
print b1,b2,b3









    



True False True



In [32]:

    
not True









    Out[32]:





False

More on Integer

Because Python has arbitrarily large integers, there will not be integer overflow happened. An an integer overflow occurs when an arithmetic operation attempts to create a numeric value that is outside of the range that can be represented with a given number of bits – either larger than the maximum or lower than the minimum representable value. Integer can also be defined using octal or hexadecimial notation, theyare the same thing from the computer point-of-view



In [5]:

    
# Octal integers
a = 01
b = 027
c = 06645
print a,"is a",type(a)

# Hexadecimal integers
a = 0x1
b = 0x17
c = 0xDA5 
print b,"is a",type(b)









    



1 is a <type 'int'>
23 is a <type 'int'>



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