Date types in python

There are various data types in Python. Some of the important types are listed below.

1. Number 
2. String.
3. List
4. Tuple
5. Set
6. Dictionary

Number

     there are mainly 3 types which include Integer, Float, and Complex.

x = 2   # int
y= 2.8  # float
z= 3j   # complex

print(type(x))

priprint(type(y))

print(type(z))

Out put 

<class ‘int’>

<class ‘float’>

<class ‘complex’>

String

          Like many other popular programming languages, strings in Python are arrays of bytes representing unicode characters. However, Python does not have a character data type, a single character is simply a string with a length of 1.

Strings are lists of characters. Any character that you can type from a computer keyboard, plus a variety of other characters, can be elements in a string. Strings are created by enclosing a sequence of characters within a pair of single or double quotes. Examples of strings include  "marylyn","omg", "good_bad_#5f>!", "{0:0.8g}", and "We hold these truths ...".  Caution: the quotes defining a given string must both be single or both be double quotes.

Strings can be assigned variable names

a = “My name is “

b= “ Hari”

Strings can be concatenated using the “+” operator:

c= a+b

Output
My name is Hari

In forming the string c, we concatenated three strings, a, b, and a string literal, in this case a space " ", which is needed to provide a space to separate string a from b.

You will use strings for different purposes: labeling data in data files, labeling axes in plots, formatting numerical output, requesting input for your programs, as arguments in functions, etc.

Because numbers—digits—are also alpha numeric characters, strings can be made up of numbers:

Example 1

print("Hello")

print('Hello')


Out put

Hello

Hello

Example 2


>>> a = 'hello'

>>> b = 'world'
>>> a[4],b[1]
('o', 'o')
>>> id(a[4]), id(b[1]), a[4] is b[1]
(4567926352, 4567926352, True)
>>> id('')
4545673904

>>> id('')
4545673904

List

      a list is created by placing all the items (elements) inside a square bracket [ ], separated by commas.

It can have any number of items and they may be of different types (integer, float, string etc.).

# empty List

my_list = [ ]

# Integer list

my_list = [ 1,2,3,4,5,]

#List with integer and string 

my_list [ 1, “hello world “, 3,4,5]

Nested List 

my_list [ “my world” , [1’2,3,4,5], [‘a’] ]

Let’s take a simple example:

colors = ['red', 'green', 'blue', 'yellow', 'white', 'black']

Here we defined a list of colors. Each item in the list has a value(color name) and an index(its position in the list). Python uses zero-based indexing. That means, the first element(value ‘red’) has an index 0, the second(value ‘green’) has index 1, and so on.

To access an element by its index we need to use square brackets.

1. >>> colors = ['red', 'green', 'blue', 'yellow', 'white', 'black']
2. >>> colors[0]
3. 'red'
4. >>> colors[1]
5. 'green'
6. >>> colors[5]
7. 'black'

Negative indexes

Using indexing we can easily get any element by its position. This is handy if we use position from the head of a list. But what if we want to take the last element of a list? Or the penultimate element? In this case, we want to enumerate elements from the tail of a list.

To address this requirement there is negative indexing. So, instead of using indexes from zero and above, we can use indexes from -1 and below.

In negative indexing system -1 corresponds to the last element of the list(value ‘black’), -2 to the penultimate (value ‘white’), and so on.

1. >>> colors = ['red', 'green', 'blue', 'yellow', 'white', 'black']
2. >>> colors[-1]
3. 'black'
4. >>> colors[-2]
5. 'white'
6. >>> colors[-6]
7. 'red'

Tuples

A tuple is a collection which is ordered and unchangeable. In Python tuples are written with round brackets.

Tuples are stored in a single block of memory. Tuples are immutalbe so, It doesn't require extraspace to store new objects. ... It is the reason creating a tuple is faster than List. It also explains the slight difference in indexing speed is faster than lists, because in tuples for indexing it follows fewer pointers.

Example

mytuple= ("Berlin", "Paris", "Rome")
print (mytuple)
Output
(‘Berlin’, ‘Paris’,’Rome’)


print(mytuple[-1])
Output 
Rome

Once in a while, it is useful to swap the values of two variables. With conventional assignment statements, we have to use a temporary variable. For example, to swap a and b:




1
2
3


temp = a
a = b
b = temp







Tuple assignment solves this problem neatly:




1


(a, b) = (b, a)







The left side is a tuple of variables; the right side is a tuple of values. Each value is assigned to its respective variable. All the expressions on the right side are evaluated before any of the assignments. This feature makes tuple assignment quite versatile.

Naturally, the number of variables on the left and the number of values on the right have to be the same:



>>> (a, b, c, d) = (1, 2, 3)
ValueError: need more than 3 values to unpack