Every variable has a type in Python. As everything in Python is an object. Datatypes are the classes, and the variables are instances of these classes.
type is used to determine the class an object belongs to and
isinstance is used to check if an object belongs to a particular class.
>>> x = 4
>>> type(x)
<type 'int'>
>>> isinstance(x, str)
False
>>> isinstance(x, int)
True
Among many various data types in Python, these are the important types are listed below.
- integer, floats: 3, 4.5
- string: 'hello world'
- list: [4, 're', 1.4]
- tuple: (4, 5)
- set: {2, 4}
- dictionary: {1: 'one', 2: 'two'}
Integers, Floats
These are for storinng numerical data. Numerical data can be of three types: Integer, Float and Complex. Python offers all these three. But let's focus on Integer and Float only.
Python interprets the decimal digits without any prefix. For example:
>>> x = 4
>>> x
4
For binary numbers append 0b or 0B before the number representation.
>>> x = 0b111
>>> x
7
For octal numbers append 0o or 0O before the number representation.
>>> x = 0o101
>>> x
65
For hexadecimal numbers append 0x or 0X before the number representation.
>>> x = 0x101
>>> x
257
Floating points are accurate upto 15 decimal places. In representation, numbers are separated by a dot(.).
>>> x = 1.12345678910111213
>>> x
1.1234567891011122
Strings
Strings are the sequence of unicode characters. These sequence must be enclosed by single quotes, double quotes or triple quotes.
>>> x = 'hello world'
>>> x
'hello world'
>>> x = "hello world"
>>> x
'hello world'
>>> x = '''hello world'''
>>> x
'hello world'
Slicing operations are allowed only to read values from strings like:
>>> x = '''hello world'''
>>> x[6:12]
'world'
Value assignment at any index is not possible in string.
>>> x = '''hello world'''
>>> x[6] = 'W'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment
This means once a string objects is created, it cannot be changed which makes them immutable data type.
List
A list is a ordered sequence of items. The items can be of any data types.
>>> x = [1, 'hello world', 1.2]
>>> x
[1, 'hello world', 1.2]
Slicing operations and Value assignment are allowed in list.
>>> x = [1, 'hello world', 1.2]
>>> x[1] = 'world'
>>> x
[1, 'world', 1.2]
Tuple
A tuple is a sequence of items like list but with a difference that once created, it cannot be changed later. It means value assignment is not allowed, just like strings. It is defined by putting parenthesis around comma separated items.
>>> x = (2, 'hello world', 3)
>>> x
(2, 'hello world', 3)
>>> x[1] = 'world'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
Tuple is also an immutable data-type.
Set
A set is an unordered collection of unique items.
>>> x = {1, 2, 2, 3, 3, 3, 4}
>>> x
set([1, 2, 3, 4])
As sets are unordered, index access is not allowed on them.
>>> a = {1,2,3}
>>> a[1]
Traceback (most recent call last):
File "<string>", line 301, in runcode
File "<interactive input>", line 1, in <module>
TypeError: 'set' object does not support indexing
Dictionary
A dictionary is an collection of key-values pairs. They are meant to be used for accessing random key data.
>>> x = {1 : 'one', 2: 'two', 3: 'three'}
>>> x[1]
'one'
>>> x[3]
'three'
One important thing to remember about dictionary is that only immutable data-types can be keys.
This pretty much covers the basic types of data-types in python. There are more specialized data types like dates and times, queues, fixed-type arrays etc. Just like the other data types they also have some special property which comes very handy while working with real data. We will be soon exploring them.
Goodbye until then.