2. Python Fundamental Data Types

 

We take some examples before like (a=10) in this a=10 (a) is the identifier, (=) is the operator (10) is the data or value.

Identifiers

The identifier can be Variable, Function, Class, or Module.

Operators types

Arithmetic operators

Assignment operators

Comparison operators

Logical operators

Identity operators

Membership operators

Bitwise operators

Data or Values types…

Text Type:                 str

Numeric Types:        int, float, complex

Sequence Types:      list, tuple, range

Mapping Type:          dict

Set Types:                  set, frozen set

Boolean Type:          bool

Binary Types:           bytes, byte-array

None Type:                None

Identifier Rules:

1. Identifiers can only a single or a combination of letters in

lowercase (a to z)

or uppercase (A to Z)

or digits (0 to 9)

or an underscore (_).

2. An identifier cannot start with a digit but above other three are ok.

3. An identifier is case sensitive, it means A=10 and a=10 both are different. 

4. No length limit of the variable name.

5. Keywords cannot be used as identifiers. Now we have doubted what is keywords

Python keywords are special reserved words, that have specific meanings and purposes and can’t be used for anything but those specific purposes. These keywords are always available—you’ll never have to import them into your code.

Python keywords are different from Python’s built-in functions and types. The built-in functions and types are also always available, but they aren’t as restrictive as the keywords in their usage.

An example of something you can’t do with Python keywords is assign something to them. If you try, then you’ll get a SyntaxError. You won’t get a SyntaxError if you try to assign something to a built-in function or type, but it still isn’t a good idea.

Python keywords:

['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

Total 35 keywords.

 Now we going to practice these points.

1. password…ok

2. p$ssword...fail because $, not an identifier symbol.

3. password@123..fail because @ not an identifier symbol.

4. 123_password.. fail because starting letter must be a letter, not a digit.

5. all passwords..fail because no spaces on an identifier

6. password2all..ok

7. if.. fail because it’s keyword

8. _password.. ok

9. _password__123…0k

6.  password               .. it means it’s a normal variable

     _password            .. it means it’s a protected variable

     __password         ..it means it’s a private variable

     __password__    .. it means it’s a magic variable.

Keywords:

'False', 'None', 'True',

'and', 'not', 'or','is',

'if', 'elif', 'else',

'while', 'for',  'break', 'continue', 'return', 'in', 'yield'

'try', 'except', 'finally', 'raise', 'assert',

'import', 'from', 'as', 'class', 'def', 'pass',

'global', 'nonlocal', 'lambda', 'del', 'with',

'async', 'await',

All are contained the alphabet letters only, all are lower case but True, False and None are Starting with Capital letters. Switch type and do-while is not in python, int, float like not in keywords because it’s a dynamically typed programing language. we can see on windows terminal python keywords. For that, we need to enter python on terminal. Then it’s going to PVM mode. Now we enter like import keyword and enter and keyword.kwlist then enter. The result on below.

C:\Users\Surya>

C:\Users\Surya>

C:\Users\Surya>python

Python 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:43:08) [MSC v.1926 32 bit (Intel)] on win32

Type "help", "copyright", "credits" or "license" for more information.

>>> import keyword

>>> keyword.kwlist

['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

>>> 

Data types:

Now we are going to in-depth in data types, how data types in python.

int, float, complex

str

list, tuple, range

dict

set, frozen set

bool

bytes, byte array

None

There are three numeric types in Python:

int

float

complex

Variables of numeric types are created when you assign a value to them:

Example

x = 1    # int

y = 2.8  # float

z = x + yj,  # complex

To verify the type of any object in Python, use the type() function:

Example

print(type(x))            # int

print(type(y))            # float

print(type(z))            # complex

Int Data Type:

Int, or integer, is a whole number, positive or negative, without decimals, of unlimited length, called an integer number.

Example

Integers:

x = 1

y = 35656222554887711

 z = -3255522

print(type(x))            #<class 'int'>

print(type(y))            #<class 'int'>

print(type(z))            #<class 'int'>

x=342342342341235636335345234523452345235423 

this int data type in python 3.x version only but in python 2.x version it’s long int type. But now we all learning and discuss python 3.x version only. we not talking about the 2.x version because python support ended. But some idea or interview purpose.

 To assign the int value to the program we have four types are available

1. Decimal form (base-10) or (0-9)

2. Binary form (base-2) 0r (o or 1)

3. Octal form (base-8) or (o to 7)

4. Hexadecimal form (base 16) (0-9 and (‘A’ to ‘F’ or ‘a’ to ‘f’))

Decimal form:

Decimal form means base 10 or zero to 9 only like whole number system or normal numbers. Ex: a= 123456975 , b=34577588433545

Binary form:

Binary form means base 2 or zero or one only. Ex: a=0101010101 , b= 11111100111

The important point here is if we are given some number like a =1111, it, not a binary number, python default the taken number is decimal number only if we want to give a binary form then we need to add zero with ‘b’ or ‘B’ and number.

Ex: a = 0b1111 or a =0B1111

It’s consider (0b1111) on binary form and calculate like this

1x2⁰=1x1=1

1x2¹=2x1=2

1x2²=4x1=4

1x2³=8x1=8

Total =15

 Octal Form:

The octal number means base 8 or zero or seven only.

Ex: a=1234567 , b= 123341245564

The important point here is, it’s only taking zero to seven number only if we are given to eight or nine number It shows an error. And if we are given some number like a =34567, it not an octal number, python default is taken number is decimal number only if we want to give a The octal form then we need to add zero with ‘o’ or ‘O’ and number.

Ex: a = 0O1111 or a =0o56455

It’s considered (0O1111) on Octal form and calculate like this

1x8⁰=1x1=1

1x8¹=8x1=8

1x8²=64x1=64

1x8³=514x1=514

Total =587

Hexadecimal form:

Hexa decimal number means the base 16 or zero or 9 and ‘a’ to ‘f’ or ‘A’ to ‘F’.

Ex: a=12789abdef , b = dedbf

The important point here is, it’s only taking zero to nine number and (a to z or A to Z both are equal) and it’s taking (a =1o, b= 11,c =12 , d= 13,e =14, f= 15) only if we are given to after ‘f’ its show error. And if we are given some number like a =34567, it not a Hexa a decimal number, python default taken number is decimal number only if we want to give a hexadecimal number then we need to add zero with ‘x’ or ‘X’ and number.

Ex: a = 0x1111 or a =0Xedbf

It’s considered (0x1111) on the hexadecimal number and calculates like this

1x16⁰=1x1=1

1x16¹=16x1=16

1x16²=256x1=256

1x16³=4096x1=4096

Total =4369

And some more valid examples are a = 345235b, b=dfead and not valid examples are a=2342ikl ,b=54658gmp because it contains after ‘f’ alphabets.

Now we are going to discuss the conversion part

Python integer other types (Decimal, Binary, Octal, hexadecimal) taking into decimal form only. But if we want to convert these types, python has default functions that are there.

1. bin()  #for convert the decimal to binary

2. oct()   #for convert the decimal to octal

3. hex()  #for converting the decimal to hexadecimal

now we are trying to numbers, convert to binary, octal, and hexadecimal support with bin function.

bin (23)         # numbers to binary number

0b10111     #result

bin(0o23)    # octal numbers to binary number

0b10011     #result

bin(0x23)   # hexa decimal numbers to binary number

0b100011   #result

now we are trying to numbers, convert to binary, octal, and hexadecimal support with oct function.

oct(23)           # numbers to octal number

0o27   #result

oct(0b11001) # binary number to octal number

0o31   #result

oct(0o347)    # octal number to octal number (it’s not required but some idea)

0o347 #result also same

oct(0x2345e) # hexa decimal number to octal number

0o432136      #result

now we are trying to numbers, convert to binary, octal, and hexadecimal support with hex function.

hex(23)    # numbers to hexadecimal number

0x17    #result

hex(0b01101)# binary number to hexadecimal number

0xd     #result

hex(0o2467)# octal number to hexadecimal number

0x537 #result

hex(0x2467f)#hexa decimal number to hexadecimal number (it’s not required but some idea)

0x2467f          #result

Float Data Type:

Float is a whole number, positive or negative, with decimals, of unlimited length called Float number.

Example

Float:

x = 1.2

y = 356562.22554887711

z = -3255.522

print(type(x))            #<class 'float'>

print(type(y))            #<class 'float'>

print(type(z))            #<class 'float'>

 

Floating point value we can assign decimal type and exponential form or scientific notation only. We can’t assign other types. If we are trying to do it, it will give an error.

a= 3.4e3 # exponential form or scientific notation

3400.0    #Result

The advantage of this future is we can assign big value in very little space and readable also very easy.

Ex:a= 456342542345235423543246345456.56734523452354354565754  #Float type

4.563425423452354e+29 #result on  exponential form

Complex datatype:

Complex datatype only in python not another language like c,c++, or java. It special data type in python. It can be creating mathematical and engineering-based applications very easily.

Complex number syntax is (a+bj), in ‘a’ is called the real part and ‘b’ is called the imaginary part and j will be the same. never try to change 'j' letter. If we are trying to change the 'j' with another number or another letter, it’s showing an error. And

 j value is (j²=-1) or j equal to square root of minus one.

This type of representation called a complex number.

Ex: a= 10+30j

We can check the function for real number and imaginary number helping with

a= 10+30J

print(a.real)

print(a.imag)

In real part, we can assign an int or float or int other form types like (decimal, binary, octal, hexadecimal) without any issue.

In imaginary part we can assign int or float only in int other form types like (decimal, binary, octal, hexadecimal) not accepted. If trying to do it’s showing an error.

Ex:      a = 10 + 10j…ok

            a = 10.3+10.3…fail  # j is not assign

            a = 0b1101+10.4j…ok

            a =  10 + 0b1001j…fail # imaginary part not expected to binary number

            a = 0o1234+10.63j…ok

            a = 0xedf+10j.. ok

Bool datatype:

Bool datatype only represent True, False (or) Yes, No (or) ok, not-ok like. Its only allowed values are True and False, but True and False must be starting with a capital letter only.

Ex:      a =10

            b = 20

            c = a>b

            print(c) # result is False

            print (type(c)) # result is <class 'bool'>

in bool date type True represents ‘1’ and False represent ‘0’ and it’s using for athematic operations

I will cover athematic operations soon.

String datatype:

String(str) datatype means any group of letters or a single letter called a string(str).

Ex : (a to z) or (A to Z) of any words. We can assign string on multiple types

Ex:      a = ‘ram’  # single quoted string is valid

            a = “ram’’  #double the quoted-string is valid

         a = '''ram''' (or) a = """ram"""# the triple string is valid (or) triple-double string also valid

Triple quoted strings using for multi-line string but single line and the double line quoted strings we can’t use.

Ex:      a = '''rama

rama

rama'''            #valid in python

a = """rama

rama

rama"""         #valid in python

            a =       ‘rama

                         rama

                         rama’             # invalid syntax

            a =   ''rama

          rama

          rama''             # invalid syntax

In python single letter also considers 'a' as str, but in other languages, it has 'a' char data type. Python doesn’t have a char data type.

Some advantages of single-quoted, double-quoted, triple quoted strings with some examples

a = ‘rama killed by ravana’   #valid

a = "rama killed by ravana"  #valid

a = '''rama killed by ravana''' #valid

 

a = '''rama

killed

           by

   ravana'''       #valid

 

a = """rama killed by ravana""" #valid

a = """rama

       killed

                by

                   ravana""" #valid

 

a = '''rama ''killed'' 'by' ravana''' #valid

a = '''rama

                ''killed''

                           'by'  

                               ravana''' #valid

 

a = """rama ''killed'' 'by' ravana""" #valid

a = """rama

                 ''killed''

                            'by'

                                 ravana""" #valid

a = 'rama \'killed\' by ravana' #valid

If we are using this type (\'), we can create more examples but I hope understand all valid points. The string is a very important role in any language, and python language also the same priority.

Triple quoted strings uses:

1.       To define multi-line string literals

2.      To use (') and ('') as a normal character in our string

3.      To define doc-string 

        Indexing:

Take one string for indexing purpose, name = ‘krishna’ now krishna string as an indexing table looks like

 

Negative      Indexing	-7	-6	-5	-4	-3	-2	-1
Memory location	k	r	i	s	h	n	a
Positive indexing	0	1	2	3	4	5	6

 

 

 

 

 

name = ‘krishna’

print (name[0]) # result is k

print (name[4]) # result is h

print (name[8]) # result is index error because no memory location is available.

print (name[-1]) # result is a

print (name[-7]) # result is k

print (name[-19]) # result is index error because no memory location is available.

This future is only available in python, other languages are positive index only.

Slice operator:

In name only we can find that ‘slice’ word. We all know slice means, some object trying to cut parts it means slice. As the same as this operator also.

Now we are taking one string name = ‘krishna’, we are trying to do a slice of this string.

Slice syntax is [begin:end-1]

Ex: [2:6]   #it’s convert to [2:5], below table will help us.

 

Negative Indexing	-7	-6	-5	-4	-3	-2	-1
Memory location	k	r	i	s	h	n	a
Positive indexing	0	1	2	3	4	5	6

 

 

 

 

 

 

name = 'krishna'

print (name[2:6])      #result    ishn

some important points:

if we are taking begin index then it will take from starting string only. And if we are not taking end index then it will take from mentioned begin index to the total end of the string.

Ex:      name = 'krishna'

print (name[2:6])      #result    ishn

name = 'krishna'

print (name[:6])      #result    krishn

name = 'krishna'

print (name[2:])      #result    ishna

name = 'krishna'

print (name[:])      #result    krishna #it’s taking full string.

name = 'krishna'

print (name[2:100])      #result    ishna # it’s taking 2 to full string.

Note: slice operator never going to give the error.

 name = 'krishna

print (name[2:1])      #result   # it’s blank or nothing.

Now we are check some uses of slice operator, for that we take one example of string like this, company = ‘american_multinational_technology_company’, now we are trying to do changes with multiple ways in this string

company = 'american_multinational_technology_company'

print (company[:].upper())

print (company[0].upper()+company[1:22])

print (company[0:8].upper()+company[8:100])

print (company[0:-1] + company[len(company)-1].upper())

print (company[0].upper() + company[1:len(company)-1]+company[-1].upper())

 Result:

AMERICAN_MULTINATIONAL_TECHNOLOGY_COMPANY

American_multinational

AMERICAN_multinational_technology_company

american_multinational_technology_companY

American_multinational_technology_companY

String with mathematical operator with multiple ways

1. name = 'tech'+'company'

    print(name)

    techcompany # Result is ok

2. name = 'tech'+2

    print(name)

    TypeError: can only concatenate str (not "int") to str    # Result

3. name = 'tech'* 2

    print(name)

    techtech # Result is ok

4. name = 4 * 'tech'

    print(name)

    techtechtechtech # Result is ok

5. name = 'tech'* 'company'

    print(name)

    TypeError: can't multiply sequence by non-int of type 'str' # Result