Python Programming | JNTUK | UNIT 2 | Lecture 6 & 7 | Conditional & Control Statements

1. Python Programming

2. UNIT 2 : SYLLABUS
• Conditions, Boolean logic, logical operators; (Refer UNIT 1: Operators)
• ranges
• Control statements: if-else, loops (for, while); short-circuit (lazy) evaluation
• Strings and text files; manipulating files and directories, os and sys
modules; text files: reading/writing text and numbers from/to a file;
creating and reading a formatted file (csv or tab-separated).
• String manipulations: subscript operator, indexing, slicing a string;
• strings and number system: converting strings to numbers and vice versa.
Binary, octal, hexadecimal numbers

3. range function
• The range() function returns a sequence of
numbers, starting from 0 by default, and
increments by 1 (by default), and stops
before a specified number
• The range() function can be represented in
three different ways, or you can think of
them as three range parameters:
1. range(stop)
2. range(start, stop)
3. range(start, stop, step)
• start: integer starting from which the
sequence of integers is to be returned
• stop: integer before which the
sequence of integers is to be returned.
The range of integers end at stop – 1.
• step: integer value which determines
the increment between each integer in
the sequence

4. range function

5. Strings and text files
Control statements
strings and number
system
String manipulations

6. Conditional (if – else)
Conditional
execution
Alternative
execution
Chained conditionals
Nested
conditionals
• Conditions
change the flow
of program
execution
• if statement is
used in conditions
Syntax:
if condition:
statement 1
…
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4
• Another
Condition in one
condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3
Control
statements

7. Conditional (if – else)
Control
statements
Conditional
execution
• Conditions
change the flow
of program
execution
• if statement is
used in conditions
Syntax:
if condition:
statement 1
…

8. Conditional (if – else)
Control
statements
Conditional
execution
• Conditions
change the flow
of program
execution
• if statement is
used in conditions
Syntax:
if condition:
statement 1
…

9. Control
statements
Conditional
execution
Alternative
execution
Chained conditionals
Nested
conditionals
• Conditions
change the flow
of program
execution
• if statement is
used in conditions
Syntax:
if condition:
statement 1
…
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4
• Another
Condition in one
condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3
Conditional (if – else)

10. Conditional (if – else)
Control
statements
Alternative
execution
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…

11. Conditional (if – else)
Control
statements
Alternative
execution
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…

12. Conditional (if – else)
Control
statements
Conditional
execution
Alternative
execution
Chained conditionals
Nested
conditionals
• Conditions
change the flow
of program
execution
• if statement is
used in conditions
Syntax:
if condition:
statement 1
…
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4
• Another
Condition in one
condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3

13. Conditional (if – else)
Control
statements
Chained conditionals
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4

14. Conditional (if – else)
Control
statements
Chained conditionals
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4

15. Conditional (if – else)
Control
statements
Conditional
execution
Alternative
execution
Chained conditionals
Nested
conditionals
• Conditions
change the flow
of program
execution
• if statement is
used in conditions
Syntax:
if condition:
statement 1
…
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4
• Another
Condition in one
condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3

16. Conditional (if – else)
Control
statements
Nested
conditionals
• Another
Condition in one
condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3

17. Conditional (if – else)
Control
statements
Nested
conditionals
• Another
Condition in one
condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3

18. Conditional (if – else)
Control
statements
Conditional
execution
Alternative
execution
Chained conditionals
Nested
conditionals
• Conditions
change the flow
of program
execution
• if statement is
used in conditions
Syntax:
if condition:
statement 1
…
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4
• Another
Condition in one
condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3

19. Strings and text files
Control statements
strings and number
system
String manipulations

20. Loops (for , while)
Control
statements
• A loop is a programming
structure that repeats a sequence
of instructions until a specific
condition is met.
• Each repetition of the action is
known as a pass or an iteration.
• Two main loop statements are
available.
• for
• while

21. Loops (for , while)
Control
statements
• for: Executes a sequence of
statements multiple times and
reduces the code that manages the
loop variable.

22. Loops (for , while)
Control
statements
Loop Header end with colon (:)
body must be indented

23. Loops (for , while)
Control
statements

24. Loops (for , while)
Control
statements
Using else Statement with for
Loop:
• If the else statement is used with
a for loop, the else statement is
executed when the loop has
exhausted iterating the list.

25. Loops (for , while)
Control
statements
• A while loop statement in Python
programming language
repeatedly executes a target
statement if a given condition is
true.

26. Loops (for , while)
Control
statements

27. Loops (for , while)
Control
statements

28. Loops (for , while)
Control
statements
Using else Statement with while
Loop:
• If the else statement is used with
a while loop, the else statement is
executed when the condition
becomes false.

29. Loops (for , while)
Control
statements
Infinite Loop:
• A loop becomes infinite loop if a
condition never becomes FALSE.
• When using while loops because
of the possibility that this
condition never resolves to a
FALSE value.
• This results in a loop that never
ends. Such a loop is called an
infinite loop.

30. Loops (for , while)
Control
statements
Loop Control Statements:
• Loop control statements change
execution from its normal
sequence.
• Python supports the following
control statements.
o break
o continue
o pass
break: Terminates the loop statement
and transfers execution to the
statement immediately following the
loop.
continue: Causes the loop to skip the
remainder of its body and
immediately retest its condition prior
to reiterating.
pass: when a statement is required
syntactically but you do not want
any command or code to execute.

31. Loops (for , while)
Control
statements
break: Terminates the loop statement
and transfers execution to the
statement immediately following the
loop.
continue: Causes the loop to skip the
remainder of its body and
immediately retest its condition prior
to reiterating.
pass: when a statement is required
syntactically but you do not want
any command or code to execute.

32. Loops (for , while)
Control
statements
break: Terminates the loop statement
and transfers execution to the
statement immediately following the
loop.
continue: Causes the loop to skip the
remainder of its body and
immediately retest its condition prior
to reiterating.
pass: when a statement is required
syntactically but you do not want
any command or code to execute.

33. Loops (for , while)
Control
statements
break: Terminates the loop statement
and transfers execution to the
statement immediately following the
loop.
continue: Causes the loop to skip the
remainder of its body and
immediately retest its condition prior
to reiterating.
pass: when a statement is required
syntactically but you do not want
any command or code to execute.

34. Loops (for , while)
Control
statements

35. Loops (for , while)
Control
statements

36. Loops (for , while)
Control
statements

37. Loops (for , while)
Control
statements
Nested Loop:
• Python programming language
allows to use one loop inside
another loop.

38. Loops (for , while)
Control
statements
Nested Loop:
• Python programming language
allows to use one loop inside
another loop.

39. Strings and text files
Control statements
strings and number
system
String manipulations

40. Short-Circuit Evaluation
Control
statements
• The Python virtual machine
sometimes knows the value of a
Boolean expression before it has
evaluated all its operands.
• For instance, in the expression A
and B, if A is false, then so is the
expression, and there is no need to
evaluate B
• Likewise, in the expression A or B, if A
is true, then so is the expression, and
again there is no need to evaluate B.
• This approach, in which evaluation
stops as soon as possible, is called
short-circuit evaluation.

41. UNIT 2 : SYLLABUS
• Conditions, Boolean logic, logical operators; (Refer UNIT 1: Operators)
• ranges
• Control statements: if-else, loops (for, while); short-circuit (lazy) evaluation
• Strings and text files; manipulating files and directories, os and sys
modules; text files: reading/writing text and numbers from/to a file;
creating and reading a formatted file (csv or tab-separated).
• String manipulations: subscript operator, indexing, slicing a string;
• strings and number system: converting strings to numbers and vice versa.
Binary, octal, hexadecimal numbers