Python programming basics

1. PE1 Module 2
Python Fundamentals

2. 2
Introduction
 Python consists of a number of coding basics.
 What do you understand from the below code?
It may look like a foreign language.
 To make meaningful sentences in a foreign language, you must
learn its alphabet, words, and grammar.
 The same is true for a programming language. Python is a
programming language.
 To write meaningful programs, you must learn the programming
language’s semantic, syntax rules and basic elements.
 The syntax rules determine which instructions are legal.
 The semantic rules determine the meaning of the instructions.
 Basic elements are the building blocks to write the instructions.

3. 3
Python Program Basics
 Basic elements/fundamentals to create a python
program:
Variables
Identifiers
Keywords
Datatypes
Input/Output
Comments
Constants
Operators

4. 4
Variables
 Variables are containers for storing data values.

5. 5
Identifiers
 An identifier is a name given to a variable.
 Python has some rules about how identifiers can be formed
Every identifier must begin with a letter or
underscore, which may be followed by any sequence
of letters, digits, or underscores.
first
conversion
payRate
counter1
Legal
employee salary
hello!
one+two
#second
Illegal: Explain why they are illegal?

6. 6
Identifiers
 Identifiers are case-sensitive
>>> x = 10
>>> X = 5.7
>>> print(x)
10
>>> print(X)
5.7

7. 7
Keywords
 Some identifiers are part of Python itself (they are called
reserved words or keywords) and cannot be used by
programmers as ordinary identifiers
False class finally is return
None continue for lambda try
True def from nonlocal while
and del global not with
as elif if or yield
assert else import pass
break except in raise
Python Keywords

8. 8
Datatypes
 A data type represents the type of data stored into a variable
or memory.
 Python assumes the type of a variable based on the assigned
value.

9. 9
Two types of Datatypes
1. Built- in data types: The datatypes which are
already available in Python language: =>our focus
2. User-defined data types: The datatypes which
are created by programmers.

10. 10
Major built- in data types:
 int datatype: represents an integer number. An integer
number is a number with out any decimal point. Example
a=10 or b=-20
 float datatype: represents floating point numbers. A
floating number is a number that contains a decimal point.
Example a=123.45 or b=-20.25
 bool datatype: represents Boolean value. A Boolean value
is a value that can be either True or False.
 str datatype: represents string. A string is a
sequence/group of characters. String can be enclosed
inside:
Single quotes: 'Welcome to Python Programming'
Double quotes: "Welcome to Python Programming"

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 As a matter of fact, we can do various kinds of conversions
between strings, integers and floats using the built-in int,
float, and str types.
Datatype Conversion
>>> x =
10
>>>
float(x)
10.0
>>>
str(x)
'10'
>>>
>>> y =
"20"
>>>
float(y)
20.0
>>>
int(y)
20
>>>
>>> z =
30.0
>>>
int(z)
30
>>>
str(z)
'30.0'
>>>
integer  float
integer  string
string  float
string  integer
float  integer
float  string

12. 12
Datatype Conversion

13. 13
Input/Output in Python
 You can display program data to the console in
Python with print().
 The input() function pauses program execution to
allow the user to type in a line of input from the
keyboard.
 Python takes all the input as a string input by
default.

14. 14
Output in Python

15. 15
Input in Python

16. 16
Input/Output

17. 17
Input/Output

18. 18
Python Comments
 Comments are descriptions that help programmers
better understand the intent and functionality of the
program.
Using comments in programs makes our code more
understandable.
Comments can also be used to ignore some code while
testing other blocks of code.
 Comments are completely ignored by the Python
interpreter.
 Comments can be:
Single-Line Comments
Multi-Line Comment

19. 19
Single-Line Comments in Python
 In Python, we use the hash symbol # to write a single-line
comment.

20. 20
Multi-Line Comments in Python
 We can use # at the beginning of each line of comment on
multiple lines.
 We can use enclosed triple double quotes.
 We can use enclosed triple single quotes.

21. 21
Constants
 A constant is a type of variable whose value cannot be changed.
 It is helpful to think of constants as containers that hold
information which cannot be changed later.
 Python doesn’t have built-in constant types.
 By convention, Python uses a variable whose name contains all
capital letters to define a constant.

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Operators in Python
 Operators are special symbols used for specific purposes.
 Python provides many operators for manipulating data.
 Operators perform an action on one or more operands.
Arithmetical Operators
Assignment Operators
Relational Operators
Logical operators
Increment and Decrement Operators
Bitwise Operators
Membership Operators

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Python Arithmetic Operators
OperatorDescription Example
+ Addition - Adds values on either side of the
operator
10 + 20 will give 30
- Subtraction - Subtracts right hand operand
from left hand operand
10 - 20 will give -10
* Multiplication - Multiplies values on either
side of the operator
10 * 20 will give 200
/ Division - Divides left hand operand by right
hand operand
20 / 10 will give 2
% Modulus - Divides left hand operand by right
hand operand and returns remainder
20% 10 will give 0
** Exponent - Performs exponential (power)
calculation on operators
10**20 will give 10 to
the power 20
// Floor Division - The division of operands
where the result is the quotient in which the
digits after the decimal point are removed.
9//2 is equal to 4 and
9.0//2.0 is equal to 4.0

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Python Assignment Operators
Operator Description Example
= Simple assignment operator, Assigns values from right side
operands to left side operand
c = a + b will assign the
value of a + b to c
+= Add AND assignment operator, It adds right operand to the left
operand and assign the result to left operand
c += a is equivalent to
c = c + a
-= Subtract AND assignment operator, It subtracts right operand from
the left operand and assign the result to left operand
c -= a is equivalent to
c = c - a
*= Multiply AND assignment operator, It multiplies right operand with
the left operand and assign the result to left operand
c *= a is equivalent to
c = c * a
/= Divide AND assignment operator, It divides left operand with the
right operand and assign the result to left operand
c /= a is equivalent to
c = c / a
%= Modulus AND assignment operator, It takes modulus using two
operands and assign the result to left operand
c %= a is equivalent to
c = c % a
**= Exponent AND assignment operator, Performs exponential (power)
calculation on operators and assign value to the left operand
c **= a is equivalent to
c = c ** a
//= Floor Division and assigns a value, Performs floor division on
operators and assign value to the left operand
c //= a is equivalent to
c = c // a

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Python Relational Operators
Operator Description Example
== Checks if the value of two operands are equal or not, if yes
then condition becomes true.
(10 == 20) is not true.
!= Checks if the value of two operands are equal or not, if
values are not equal then condition becomes true.
(10!= 20) is true.
<> Checks if the value of two operands are equal or not, if
values are not equal then condition becomes true.
(10 <> 20) is true. This is
similar to != operator.
> Checks if the value of left operand is greater than the value
of right operand, if yes then condition becomes true.
(10 > 20) is not true.
< Checks if the value of left operand is less than the value of
right operand, if yes then condition becomes true.
(10 < 20) is true.
>= Checks if the value of left operand is greater than or equal
to the value of right operand, if yes then condition becomes
true.
(10>= 20) is not true.
<= Checks if the value of left operand is less than or equal to
the value of right operand, if yes then condition becomes
true.
(a10<= 20) is true.

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Python Logical Operators
Operator Description Example
and Called Logical AND operator. If both the
operands are true then then condition
becomes true.
(10 and 20) is true.
or Called Logical OR Operator. If any of the two
operands are non zero then then condition
becomes true.
(10 or 0) is true.
not Called Logical NOT Operator. Use to
reverses the logical state of its operand. If a
condition is true then Logical NOT operator
will make false.
not(10 and 20) is false.

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Increment and Decrement Operators
 The increment operator ++
It adds one to a variable.
 The decrement operator --
It subtracts one from a variable
 Increment and decrement operators can be used
before(prefix) or after(postfix) a variable.
 In prefix mode (++ variable or - -variable) the operator
increments or decrements, then returns the value of the
variable.
 In postfix mode (variable++ or variable- -) the operator
returns the current value of the variable, then increments or
decrements.

28. 28
Post increment Operator
 The position of the ++ determines when the value
is incremented. If the ++ is after the variable, then
the incrementing is done last (a post
increment).
 count = 3
 amount = 2 * count++
 amount gets the value of 2 * 3, which is 6, and then
1 gets added to count.
 So, after executing the last line, amount is 6 and
count is 4.

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Pre increment Operator
 If the ++ is before the variable, then the
incrementing is done first (a pre increment).
 count = 3
 amount = 2 * ++count
 1 gets added to count first, then amount gets the
value of 2 * 4, which is 8.
 So, after executing the last line, amount is 8 and
count is 4.

30. 30
Post decrement Operator
 The position of the -- determines when the value is
decremented. If the -- is after the variable, then
the decrementing is done last (a post
decrement).
 count = 3
 amount = 2 * count--
 amount gets the value of 2 * 3, which is 6, and
then 1 gets subtracted from count.
 So, after executing the last line, amount is 6 and
count is 2.

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Pre decrement Operator
 If the -- is before the variable, then the
decrementing is done first (a pre decrement).
 count = 3
 amount = 2 * --count
 1 gets subtracted from count first, then amount
gets the value of 2 * 2, which is 4.
 So, after executing the last line, amount is 4 and
count is 2.

32. 32
Python Bitwise Operators
Operator Description Example
& Binary AND Operator copies a bit 1 to the
result if it exists in both operands.
(60& 13) will give 12 which
is 0000 1100
| Binary OR Operator copies a bit 1 if it exists in
either operand.
(60 | 13) will give 61 which
is 0011 1101
^ Binary XOR Operator sets the bit to 1 if the bit
of the operand opposite.
(60^ 13) will give 49 which
is 0011 0001
~ Binary Ones Complement Operator is unary
and has the effect of 'flipping' bits.
(~60 ) will give -60 which
is 1100 0011
<< Binary Left Shift Operator. The left operands
value is moved left by the number of bits
specified by the right operand.
60<< 2 will give 240 which
is 1111 0000
>> Binary Right Shift Operator. The left operands
value is moved right by the number of bits
specified by the right operand.
60>> 2 will give 15 which
is 0000 1111

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Python Membership Operators
In addition to the operators discussed previously, Python has
membership operators, which test for membership in a sequence,
such as strings, lists, or tuples.
Operator Description Example
in Evaluates to true if it finds a variable in the
specified sequence and false otherwise.
x in y, here in results in a 1 if
x is a member of sequence y.
not in Evaluates to true if it does not finds a variable
in the specified sequence and false otherwise.
x not in y, here not in
results in a 1 if x is a member
of sequence y.

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Python Operators Precedence
Operator Description
() ++ - - ** Parentheses, increment, decrement, exponentiation
~ complement
* / % // Multiply, divide, modulo and floor division
+ - Addition and subtraction
>> << Right and left bitwise shift
& Bitwise 'AND'
^ | Bitwise exclusive `OR' and regular `OR'
<= < > >= Comparison operators
<> == != Equality operators
= %= /= //= -= += *=
**=
Assignment operators
is is not Identity operators
in not in Membership operators
not or and Logical operators

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Any Question?
Thank You!