Types in Python

Introduction to Types in Python

In general, the structure of a Python program is as follows:

Programs are composed of modules.

Modules contain statements.

Statements contain expressions.

Expressions create and process objects.

In Python, everything is an object. Including values. Even simple numbers qualify, with values (e.g., 99), and supported operations (addition, subtraction, and so on). In Python, data takes the form of objects—either built-in objects that Python provides, or objects we create using Python classes or external language tools such as C extension libraries.

Following table shows fundamental Python’s built-in object types and some of the syntax used to code their literals—that is, the expressions that generate these objects:

Object Type	Examples
Numbers	12, 2.67, 6+8j, 0b1011
Strings	‘hai’, “hello”, “Python’s Features”, str(‘Python’)
Lists	[1,2,3], [1,2,’three’], list(range(10)), list(‘hai’)
Tuples	(1,2,3), (1,2,’three’), tuple(range(10)), tuple(‘hai’)
Sets	{1,2,3}, set(‘hai’)
Dictionaries	{‘Mon’:1, ‘Tue’:2, ‘Wed’:3}, dict(hours=10)

Following are some more types available in Python:

Object Type	Examples
Files	open(‘abc.txt’)
Functions	def, lambda
Modules	import, __module__
Classes	objects, types, metaclasses
None	None
Booleans	True, False

In this article we will learn about Number and Boolean types. We will learn about other types in other articles.

Numbers

Numbers include the following:

integers
floating-point numbers
complex numbers
decimals with fixed precision
rational numbers with numerator and denominator
sets

Using third party extensions we have more types like matrices, vectors, etc.

Following are examples of numeric literals and constructors:

Literal	Description
12, -887, 0, 999999999999999999999998	Integers (unlimited size)
1.23, 1., 3.14e-10, 4E210, 4.0e+210	Floating-point numbers
0o177, 0x9ff, 0b101010	Octal, hex, and binary literals
6+4j, 2.0+9.0j, 7J	Complex number literals
Decimal(‘13.0’), Fraction(4, 7)	Decimal and fraction extension types
bool(X), True, False	Boolean type and constants

Floating-point numbers are implemented as C doubles in standard Cpython. The functions hex, oct, and bin can be used to convert integers to hexadecimal, octal, and binary formats respectively.

Complex numbers are internally implemented as pairs of floating-point numbers. Complex numbers can be ended with j or J. Complex numbers can also be created with complex(real, imag) function call.

We can use built-in functions like: pow, abs, round, int, hex, bin, etc on numbers. We can also use utility modules like random, math as follows:

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>>> import random

>>> random.random()

0.865758460309634

>>> random.choice(range(100))

96

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>>> import math

>>> math.sqrt(7)

2.6457513110645907

Decimals

Decimals are fixed precision floating point numbers. Decimals can be precise up to n digits after the decimal point. For example, 0.1+0.1+0.1-0.3 gives 5.551115123125783e-17. In such cases, we can use decimal as follows:

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>>> from decimal import Decimal

>>> x=Decimal('0.1')

>>> y=Decimal('0.3')

>>> x+x+x-y

Decimal('0.0')

Default precision for decimal is 28 digits. We can set the precision as follows:

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>>> import decimal

>>> decimal.Decimal(1) / decimal.Decimal(7) 

Decimal('0.1428571428571428571428571429')

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#Set precision to 4 digits

>>> decimal.getcontext().prec = 4 

>>> decimal.Decimal(1) / decimal.Decimal(7)

Decimal('0.1429')

Fraction

Fraction objects are used to implement rational numbers. It keeps both numerator and denominator explicitly. Following are examples for working with fractions in Python:

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>>> from fractions import Fraction

>>> x=Fraction(2,7)

>>> y=Fraction(3,7)

>>> x+y 

Fraction(5, 7)

>>> x*y

Fraction(6, 49)

>>> print(x)

2/7

Booleans

Python provides Boolean data type called bool with values True and False. True represents integer 1 and False represents integer 0. bool is a sub class of integer class. Following are examples on Booleans:

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>>> True == 1

True

>>> True is 1

False

>>> True and False

False

>>> True + 10

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>>> False * 9

0

NETAJI

Types in Python

Introduction to Types in Python

Numbers

Decimals

Fraction

Booleans

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