Parts of python programming language

Parts of Python
Programming language
Megha V
Research Scholar
Kannur University
31-10-2021 meghav@kannuruniv.ac.in 1

Parts of Python Programming language
• Keywords
• statements and expressions
• Variables
• Operators
• Precedence and Associativity
• Data Types
• Indentation
• Comments
• Reading Input
• Print Output

Keywords
Keywords are the reserved words that are already defined by the Python for
specific uses
• False await else import pass
• None break except in raise
• True class finally is return
• and continue for as assert
• async def del elif from
• global if lambda try not
• or while with yield

Variables
• Reserved memory locations to store values.
• It means that when you create a variable, you reserve some space in
the memory.
counter = 100 # An integer assignment
miles = 1000.0 # A floating point
name = "John" # A string
print (counter)
print (miles)
print (name)

Multiple Assignment
• Python allows you to assign a single value to several variables
simultaneously.
a = b = c = 1
• You can also assign multiple objects to multiple variables
a, b, c = 1, 2, "john”

Operators
Python language supports the following types of operators-
• Arithmetic Operators
• Comparison (Relational) Operators
• Assignment Operators
• Logical Operators
• Bitwise Operators
• Membership Operators
• Identity Operators

Arithmetic Operators
• Assume a=10 ,b =21, then
Operator Description Example
+ Addition Adds values on either side of the operator. a + b = 31
- Subtraction Subtracts right hand operand from left hand
operand.
a – b = -11
* Multiplication Multiplies values on either side of the operator a * b = 210
/ Division Divides hand operand by right hand operand left b / a = 2.1
% Modulus Divides left hand operand by right hand operand
and returns remainder
b % a = 1
** Exponent Performs exponential (power) calculation on
operators
a**b =10 to the
power 21
// Floor Division 9 - The division of operands where the result is the
quotient in which the digits after the decimal point
are removed.
//2 = 4 and 9.0//2.0
= 4.0

Comparison Operators/ Relational operators
• These operators compare the values on either side of them and decide the relation among them.
• Assume a =10 , b=20, then
Operator< Description Example
== If the values of two operands are equal, then the condition become true (a==b) is not
true
!= If values of two operands are not equal, then condition become true (a!=b) is true
> If the value of the left operand is greater than the value of the right operand,
then condition become true
(a>b) is not
true
< If the value of the left operand is less than the value of the right operand, then
condition become true
(a<b)is true
>= If the value of the left operand is greater than or equal to the value of the right
operand, then condition become true
(a>=b)is not
true
<= If the value of the left operand is less than or equal to the value of the right
operand, then condition become true
(a<=b)is true

Logical operators
Precedence of logical operator
• not –unary operator
• and Decreasing order
• or
Example
>>> (10<5) and ((5/0)<10)
False
>>> (10>5) and ((5/0)<10)
ZeroDivisionError

Bitwise operators
• Bitwise AND – x & y
• Bitwise OR – x|y
• Bitwise Complement - ~ x
• Bitwise Exclusive OR -x˄y
• Left Shift – x<<y
• Right Shift –x>>y

Precedence and Associativity of operators
Operator
Decreasing
order
()
**
+x, -x, ~x
/, //, *, %
+, -
<<, >>
&
˄
|
==,<, >, <=, >= , !=
not
and
or

Data Types
Python has five standard data types-
• Numbers
• String
• List
• Tuple
• Dictionary

Numbers
• Number data types store numeric values.
• Number objects are created when you assign a value to them.
• For example
var1 = 1 var2 = 10
• Python supports three different numerical types
- int (signed integers)
- float (floating point real values)
- complex (complex numbers)

Strings
• Continuous set of characters represented in the quotation
marks.
• Python allows either pair of single or double quotes.
• Subsets of strings can be taken using the slice operator ([ ] and
[:] ) with indexes starting at 0 in the beginning of the string and
working their way from -1 to the end.
• The plus (+) sign is the string concatenation operator and the
asterisk (*) is the repetition operator.

Strings
For example-
str = 'Hello World!’
print (str) # Prints complete string – Hello World!
print (str[0]) # Prints first character of the string - H
print (str[2:5]) # Prints characters starting from 3rd to 5th- llo
print (str[2:]) # Prints string starting from 3rd character –llo World!
print (str * 2) # Prints string two times –Hello World! Hello World!
print (str + "TEST") # Prints concatenated string- Hello World!Test

Lists
• Lists are the most versatile of Python's compound data types.
• A list contains items separated by commas and enclosed within square
brackets ([]).
• To some extent, lists are similar to arrays in C.
• One of the differences between them is that all the items belonging to a list
can be of different data type.
• The values stored in a list can be accessed using the slice operator ([ ] and
[:]) with indexes starting at 0 in the beginning of the list and working their
way to end -1.
• The plus (+) sign is the list concatenation operator, and the asterisk (*) is
the repetition operator.

Lists
For example
list = [ 'abcd', 786 , 2.23, 'john', 70.2 ]
tinylist = [123, 'john’] Output
print (list) # Prints complete list
print (list[0]) # Prints first element of the list
print (list[1:3]) #Prints elements starting from 2nd till 3rd
print (list[2:]) # Prints elements starting from 3rd element
print (tinylist * 2) # Prints list two times
print (list + tinylist) # Prints concatenated lists

Tuples
• Similar to the list.
• Consists of a number of values separated by commas.
• Enclosed within parenthesis.
• The main difference between lists and tuples is-
• Lists are enclosed in brackets ( [ ] ) and their elements and size can be
changed, while tuples are enclosed in parentheses ( ( ) ) and cannot
be updated.
• Tuples can be thought of as read-only lists.

Tuples
For example-
tuple = ( 'abcd', 786 , 2.23, 'john', 70.2 )
tinytuple = (123, 'john’) Output
print (tuple) # Prints complete tuple
print (tuple[0]) # Prints first element of the tuple
print (tuple[1:3]) # Prints elements starting from 2nd till 3rd
print (tuple[2:]) # Prints elements starting from 3rd element
print (tinytuple * 2) # Prints tuple two times
print (tuple + tinytuple) # Prints concatenated tuple
tuple = ( 'abcd', 786 , 2.23, 'john', 70.2 )
list = [ 'abcd', 786 , 2.23, 'john', 70.2 ]
tuple[2] = 1000 # Invalid syntax with tuple
list[2] = 1000 # Valid syntax with list

Dictionary
• Python's dictionaries are kind of hash-table type.
• They work like associative arrays or hashes found in Perl and consist
of key-value pairs.
• A dictionary key can be almost any Python type, but are usually
numbers or strings. Values, on the other hand, can be any arbitrary
Python object.

Dictionary
• Dictionaries are enclosed by curly braces ({ }) and values can be assigned and accessed
using square braces ([]).
For example-
dict = {}
dict['one'] = "This is one"
dict[2] = "This is two"
tinydict = {'name': 'john','code':6734, 'dept': 'sales’} Output
print (dict['one']) # Prints value for 'one' key
print (dict[2]) # Prints value for 2 key
print (tinydict) # Prints complete dictionary
print (tinydict.keys()) # Prints all the keys
print (tinydict.values()) # Prints all the values

Indentation
• Adding white space before a statement
• To indicate a block of code.
if 5 > 2:
print("Five is greater than two!")
if 5 > 2:
print("Five is greater than two!") #syntax error
if 5 > 2:
print("Five is greater than two!")
print("Five is greater than two!") # syntax error

Comments
• A hash sign (#) that is not inside a string literal is the beginning of a
comment.
• All characters after the #, up to the end of the physical line, are part
of the comment and the Python interpreter ignores them.
• # First comment
• print ("Hello, Python!") # second comment

Reading Input
• Python provides some built-in functions to perform both input and output
operations.
Python provides us with two inbuilt functions to read the input from the
keyboard.
raw_input()
input()
raw_input(): This function reads only one line from the standard input and returns
it as a String.
input(): The input() function first takes the input from the user and then evaluates
the expression, which means python automatically identifies whether we entered a
string or a number or list.
• But in Python 3 the raw_input() function was removed and renamed to input().

Print Output
In order to print the output, python provides us with a built-in function called
print().
Example:
Print(“Hello Python”)
Output:
Hello Python

Type conversion
• Python defines type conversion functions to directly convert one data
type to
1. int(a,base) # any data type to integer. ‘Base’ specifies the base in which string
is if data type is string.
2. float() #any data type to a floating point number
3. ord() #character to integer.
4. hex() #integer to hexadecimal string.
5. oct() #integer to octal string.
6. tuple() #convert to a tuple.
7. set() #returns the type after converting to set.
8. list() # any data type to a list type
10. str() # integer into a string.
11. complex(real,imag) # real numbers to complex(real,imag) number.
12. chr(number) #number to its corresponding ASCII character.

is operator
• The Equality operator (==) compares the values of both the operands and checks for
value equality.
• Whereas the ‘is’ operator checks whether both the operands refer to the same object or
not (present in the same memory location).

Dynamic and Strongly typed language
• Python is a dynamically typed language.
• What is dynamic?
• We don't have to declare the type of a variable or manage the
memory while assigning a value to a variable in Python.

Mutable and immutable objects in Python
• There are two types of objects in python i.e.
• Mutable and Immutable objects.
• Whenever an object is instantiated, it is assigned a unique
object id.
• The type of the object is defined at the runtime and it can’t be
changed afterwards.
• However, it’s state can be changed if it is a mutable object.
• Immutable Objects : These are of in-built types like int, float,
bool, string, unicode, tuple. In simple words, an immutable
object can’t be changed after it is created.
• Mutable Objects : These are of type list, dict, set . Custom
classes are generally mutable.

Parts of python programming language

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