Conditional Expressions
Conditional Expressions
Sometimes we want to play pubg on our phone if the day is Sunday.
Sometimes we order Ice-cream online if the day is sunny.
Sometimes we go hiking if our parents allow.
All these are decisions that depend on the condition being met.
In python programming too, we must be able to execute instructions
on a condition(s) being met. This is what conditions are for!
If else and elif in Python
If else and elif statements are a multiway decision taken by our
program due to certain conditions in our code.
Syntax:
'''
if
(condition1): //
if condition 1 is true
print(“yes”)
elif
(condition2): //
if condition 2 is true
print(“No”)
else: //
otherwise
print(“May
be”)
'''
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Code example:
a = 22
if (a>9):
print(“Greater”)
else:
print(“lesser”)
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Quick Quiz: Write a program to print
yes when the age entered by the user is greater than or equal to 18.
Relational Operators
Relational operators are used to evaluate conditions inside if
statements. Some examples of relational operators are:
= = -> equals
>= ->
greater than/equal to
<=, etc.
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Logical Operators
In python, logical operators operate on conditional statements.
Example:
and -> true if both operands are
true else false
or -> true if at least one
operand is true else false
not -> inverts true
to false and false to true
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elif clause
elif in python means [else if]. If statement can be chained
together with a lot of these elif statements followed by an else statement.
'''
if (condition1):
#code
elif (condition 2):
#code
elif (condition 2):
#code
….
else:
#code '''
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- The above ladder
will stop once a condition in an if or elif is met.
Important Notes:
- There can be any
number of elif statements.
- Last else is
executed only if all the conditions inside elifs fail.
Chapter 6 – Practice Set
1.
Write a program to find the greatest of four numbers entered by
the user.
2.
Write a program to find out whether a student is pass or fail if
it requires a total of 40% and at least 33% in each subject to pass. Assume 3
subjects and take marks as an input from the user.
3.
A spam comment is defined as a text containing the following
keywords:
“make a lot of money”, “buy now”, “subscribe this”, “click this”.
Write a program to detect these spams.
4.
Write a program to find whether a given username contains less
than 10 characters or not.
5.
Write a program that finds out whether a given name is present in
a list or not.
6.
Write a program to calculate the grade of a student from his marks
from the following scheme:
|
90-100 |
Ex |
|
80-90 |
A |
|
70-80 |
B |
|
60-70 |
C |
|
50-60 |
D |
|
<50 |
F |