Session 1 Python Programming slide series is part of Object-Oriented System Analysing & Designing in CS.QIAU Undergrad.

1. CS.QIAU - Winter 2020
PYTHONBasic Parts - Session 1
Omid AmirGhiasvand
Programming

2. Identifier
▸ Is a name given to a variable, function, class or module.
▸ Can only contain letter and number and underscore.
▸ my_list_11
▸ They can start just with letter or underscore.
▸ Space are not allows in variable name.
▸ use underscore instead
▸ Python keywords can not be used as identifiers.
▸ Python is case sensitive.
▸ “Name” and “name” are 2 different identifiers!

3. ▸ Always use meaningful name for identifier.
Identifier
Identifier Valid Not Valid
Good Bad
name
17name
%name
x
students_list
x-list
for
teacher id
Best Practice
Keyword
space

4. Keywords
▸ Keywords are a list of reserved words that have predefined meaning.
Python Keywords
def with in True
return for is False
class while and None
break if or global
continue elif not nonlocal
try else as from
except pass import
finally assert raise

5. Statements and Expression
▸ A Statement is an Instruction that the Python Interpreter can execute.
▸ welcome_message=“Welcome To Python”
▸ A Python Program consist of a sequence of statements.
▸ An statement can be one or several line of code.
▸ Expression is an arrangement of values and operators which are
evaluated to make a new value.
▸ Expressions are statements as well.
▸ total_payment = monthly_rate * 12
assignment statement

6. Variable
▸ Variable are used in programming language to hold value.
▸ The variable’s value is actually the Information associated with that variable
name.
▸ variable = expression or single value
▸ age = 0
▸ age = 11 * 3
▸ payment = h_rate * 100
36age Memory
Location
variable
name

7. Naming Convention
▸ Compare these two statements:
▸ S1
▸ S2
1. c = a * b
1. weekly_pay = hours_worked * hourly_pay_rate
Best Practice

8. ▸ Arithmetic operators are used to execute arithmetic operations
Arithmetic Operators
Operator Operator Name Example
+ Additional 3 + 5
- Subtraction 3 - 5
* Multiplication 3 * 5
/ Division 7 / 3
% Modulus 7 % 3
** Exponent 2 ** 10
// Floor division 7 // 3
result is 2

9. ▸ Arithmetic Assignment operators are used for assigning the values
generated after evaluating the right operand to the left operand
Assignment Operators
Operator Operator Name Example
.= Assignment age = 21
+= Additional Assignment age +=2
-= Subtraction Assignment age -=2
*= Multiplication Assignment age *=age
/= Division Assignment result /=2
**= Exponential Assignment k **= 10
//= Floor Division Assignment result //=2
%= Reminder Assignment result %=2
Variable must be initialized before used

10. ▸ Arithmetic Assignment operators are used for assigning the values
generated after evaluating the right operand to the left operand
Comparison Operators
Operator Operator Name Example
.== Equal to age == 21
!= Not Equal to age != -1
> Greater Than age > 18
< Lesser Than age < 35
>= Greater Than or Equal to age >= 30
<= Lesser Than or Equal to age <= 29

11. ▸ The logical operators are used for comparing or negating the logical
values of their operands and to return results logical value
Logical Operators
Operator Operator Name Example
and Logical AND age > 18 and sex==male
or Logical OR age > 18 or sex==male
not Logical NOT not age > 12

12. Precedence
▸ Operator precedence determines the way in which operators are
parsed with respect to each other.
Operator Operator Name
() Parantheses
** Exponent
+x,-x Unary Plus, Unary Minus
*,/,//,% Multiplication, Division, Floor division, Modulus
+,- Addition, Subtraction
!=,==,>=,<=,>,< Comparisons
in, is, not in, is not Identity, Membership operators
not Logical NOT
and Logical AND
or Logical OR
Operators with higher precedence become the operands of operators with lower precedence.

13. Data Types
▸ Strings
▸ className=“Python Programming”
▸ Number
▸ age = 22
▸ avg = 12.45
▸ Boolean
▸ male = False
▸ None - The absence of value
▸ validEmail = None
All numbers are True and just 0 is False

14. built-in
function

16. IN PYTHON THERE
IS NO ; OR { }
Not like Java or C++

17. Indentation & Blocks
▸ In Python, Programs get structured through indentation
In Python indentation is a requirement and not
a matter of style or convention
Block 1
Block 1 - Continue
Block 2
Block 2 - Continue
Block 3

18. Comments
▸ Allow you to write comments and notes and also disable some part of
your code.
▸ Comment Types
▸ Single-line: Hash mark indicate single line comments. Anything follow # is
ignored by the python compiler/interpreter
▸ Multi-line comment using ‘’’ … ‘’'
1. #This is a single line comment
2. ‘’’ Start of multi-line commenting
3. …
4. …
5. End of multi-line commenting’’’
3 single
quotation

19. Input/Output
▸ In Python, input() function is used to gather data from the user.
▸ The print() function allows a program to display text onto the console.
1. name = input(“Enter your name:”)
1. print(f”your name is {name}”)
f-string
variable or
expression

20. Formatted String
▸ Formatted String or f-strings were introduced in Python 3.6
▸ f-string is a string literal that is prefixed with “f”.
▸ The string may contain replacement fields.
▸ which are expressions enclosed within curly braces {}

21. Using f-string
formatting

22. Type Conversions
▸ You can explicitly cast or convert a variable from one type to another.
▸ int()
▸ str()
▸ float()
▸ chr()
age = int(value)
cast to
int

23. Casting
input function
return string
real_age is int
after casting

24. input and
casting in one line
age is int

25. you can not
subtract from str
Exception
age is str

26. DISCOVERFOR YOURSELF
Change things and see what will happens. Noting going to BREAK :)

27. “The Unexamined Life Is Not Worth Living”