The document discusses various topics in Python programming including literal constants, numbers, strings, variables, data types, operators, and expressions. It defines literal constants as values that cannot be changed and lists examples. It describes the different number types in Python and issues with floating point numbers. It also covers formatting numbers, simple numeric operations, strings, variable naming rules, data types, assigning values, comments, and indentation in Python code.

1. 20BCT23 – PYTHON PROGRAMMING

2. Literal Constants and Numbers
• Literal Constants:
– The value of a literal constant can be used directly in programs.
– Eg : 7,3,9,’A’ and “Hello” are literal constants.
– It is a constant because its value cannot be changed.
• Numbers:
– Four types of nunmbers in Python.
– Integers – 5 or other whole numbers.
– Long Integers- 535633629843L or other bigger whole numbers.
– Complex Numbers – Number of the form a+bi
• Issues in floating point numbers:
– The arithmetic overflow problem.
– The arithmetic underflow problem.
– Loss of precision problem.

3. Format() function
• format (float(16/(float(3))),’.2f’)
– ‘5.33’
• format(float(16/3),’.2f’)
– ‘5.33’
• format(3**50,’.5e’)
– ‘7.17898e+23’
• format(123456, ’ , ’)
– ‘123,456’

4. Simple operations on Numbers
• 10+7 #17
• 50+40-35 #55
• 12*10 #120
• 96/12 #8.0
• 96//12 #8
• (-30*4)+500 #380
• -15/0 #Zero Division Error
• 5*3.0 #15.0
• 78%5 #3
• 152.78//3.0 #50.0
• 152.78/3.0 #2.780000000000001
• 36**0.5 #6.0
• 78//5 #15

5. Strings
• String are group of characters
• Strings can e represented
– Using single quotes Eg: ‘Hello’
– Using double quotes Eg: “Hello” same as ‘Hello’
– Using triple quotes – Eg: ‘’’Hello’’’ To specify multi-line.
• print(‘Hello’) #Hello
• print(“Hello”) #Hello
• print(‘ “Hello” ’) #”Hello”
• print(“ ‘Hello’ ”) #’Hello’
• print(‘ ’ ’ “Hello” ‘ ‘ ‘) #”Hello”
• print(‘’’ ‘Hello’ ’’’) #’Hello’

6. Strings
• String Literal Concatenation:
– print(‘Hello’ ‘ ‘ ‘ World!’) # Hello World!
• Unicode Strings:
– Standard way of writing international text.
– To write text in native language need to enable unicode text editor.
– U” Sample Unicode String” # ‘Sample Unicode String’
• Escape Sequence:
– Some characters like “, cannot be directly included in a string.
– Such characters must be escaped by placing a backslash before them.
– Eg: print(‘What’s your Name’) # Invalid Syntax
print(‘What’s your Name’) # What’s your Name
• Raw String:
– In order to specify a string that should not handle any escape sequences and
to display exactly as specified raw string.
– print(R’What’s Your Name’) # What’s Your Name

7. Variable and Identifiers
• Variables means its value can vary.
• It is just parts of computer’s memory where information is stored.
• Variables are reserved memory locations that stores values.
• Identifiers are names given to identify something like variables,
function, class, module or other object.
• Basic rules for naming identifiers,
• First character must be an ‘_’ or a letter.
• Rest of the identifier can be ‘_’ or letters or numbers.
• Identifier names are case sensitive.
• Punctuation characters such as @,$ and % are not allowed within
identifiers.
• Valid: sum, _var,num1,r
• Invalid: 1num,my-var,%check

8. Data Types
• Variable can held values of different types are
called data types.
• Based on the data types of a variable, the
interpreter reserves memory for it and also
determines the type of data that can be stored in
the reserved memory.
– Basic Types: Numbers and Strings
– Own Data Type : Classes
– Standard Data Type: numbers, string, list, tuple and
dictionary.

9. Assigning Values to the Variables
• Need not explicitly declare variables.
• Declaration is done when the value is assigned.
• Eg : x=‘a’
• In python, varaibles may be reassigned as many times as
possible to change the value stored in them.
Val=“hello”
print(val)
• Multiple Assignment:
– Python allows programmers to assign a single value to more
than on variables simultaneously.
• Eg : sum,a,b,msg=0,3,5,”Result”
– Trying to reference a variable that has not been assigned any
value causes an error.

10. Data Types
• Boolean:
– Boolean variables have one of the two values. True or False
– Eg : Flag=True 20!=20
• Input Operation:
– The input function takes user’s input as a string.
– Python uses input() functionto take input from user.
– Eg: age=input(“Enter Your Age”)
• Comments:
– Comments are non executable statements in a program.
– Makes the program easily readable and understandable by the
programmer as well as others who are seeing the code.
– # a hash sign represents comment line.
– print(“Hello”) #prints the string Hello

11. • Reserved Words:
– These words have a pre-defined meaning .
– Cannot be used for naming identifiers.
– Eg : and assert break class exec finally for from not
• Indentation:
– White space at the beginning of the line is called indentation.
– Single tab for each indentation level.
– It is used to associate and group statements.
– The level of indentation groups statements to form a block of
statements.
– The statements in a block should have same indentation level.
– Error is thrown if indentation is not correct.
– Eg : age=21
print(age) # Indentation Error
– All the statement inside the block should be at the same
indentation level.

12. Operators and Expressions
• Operators are the constructs that are used to manipulate the value of
operands.
• Eg: sum=a+b
• Arithmetic Operator:
• +,-,*,/,//,%,**,|,&
• Comparison Operator:
– These are also called as relational operator.
– Used to compare the values on its either sides and determine the relationship between
them.
– Eg: a==b a!=b a>b
– ==,!=,>,<,>=,<=
• Shortcut operators :
– +=,-=,*=,/=,%=
• Unary operator:
– Acts on single operands.
– When an operand is preceded by a minus sign, the unary operator negates its value.
– Eg : b=-10 a=-b #a=10