CS 110

If, else, and elif

Benjamin Dicken

Harvard Study ( See: https://phys.org/news/2019-09-students-classrooms.html )

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if-else

What pair of inputs would cause only "Workload OK" to print ?

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title = input('Job title: ')

hours = int(input('Hours worked per week: '))

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if title != 'manager' and hours > 20:

if title == 'waiter':

print('Workload too high')

else:

print('Workload OK')

if hours > 40:

print('Reduce hours')

else:

print('Acceptable hours')

Activity

if-else

Possible to print both "Workload OK" and "Reduce hours" ?

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title = input('Job title: ')

hours = int(input('Hours worked per week: '))

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if title != 'manager' and hours > 20:

if title == 'waiter':

print('Workload too high')

else:

print('Workload OK')

if hours > 40:

print('Reduce hours')

else:

print('Acceptable hours')

Activity

if-else

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Use the if statement to execute code in the True case

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Can add an else to specify code to run in the False case

statements . . .

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if condition:

statement 1a

statement 2a

. . .

statement Na

else:

statement 1b

statement 2b

. . .

statement Nb

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statements . . .

​

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What are all of the inputs that will cause only “No need to retire yet” to print?

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age = int(input('Enter age:'))

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if age > 18:

if age > 65:

print('Are you retired yet?')

else:

print('No need to retire yet.')

if age < 25:

print('Why retire?')

else:

print('Wait until you are an adult')

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Activity

String comparison

• Compares alphabetically, one character at-a-time, left-to-right

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'albatross' == 'albertson'

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What is the result?

String comparison

• Compares alphabetically, one character at-a-time, left-to-right

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'albatross' <= 'albertson'

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What is the result?

String comparison

• Compares alphabetically, one character at-a-time, left-to-right

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'albatross' <= 'albERTSON'

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What is the result?

Provide one pair of inputs to print “Workload too high”

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title = input('Job title: ')

hours = int(input('Hours worked per week: '))

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if title >= 'chair' and title <= 'wait':

if title != 'busser':

print('Workload too high')

else:

print('Workload OK')

if hours > 50:

print('Reduce hours')

else:

print('Acceptable hours')

​

​

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Activity

if-else

Provide one pair of inputs that would cause “Not acceptable” to print out

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age = int(input('Enter age:'))

citizenship = input('Enter citizenship:'))

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if citizenship < 'i' and (age >= 15 or citizenship > 't'):

print('You can join the club')

else:

print('Not acceptable')

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Activity

elif

• You can follow an if with zero or more elif statements
• With elif statements, you provide a condition as you do with an if statement
• A chain of if/elif will be followed until it reaches a condition that evaluates to True
• One such a condition is reached, python will execute the body of that particular if or elif and then continue on after the chain.

statements . . .

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if conditionA:

statements

elif conditionB:

statements

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statements . . .

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statements . . .

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if conditionA:

statements

elif conditionB:

statements

elif conditionC:

statements

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statements . . .

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​

statements . . .

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if conditionA:

statements

elif conditionB:

statements

elif conditionC:

statements

elif conditionD:

statements

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statements . . .

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​

statements . . .

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if conditionA:

statements

elif conditionB:

statements

elif conditionC:

statements

else:

statements

​

statements . . .

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Write the program

• Accepts a number as input
• Prints out the letter grade that you will receive

What is your numeric grade? 97

You will get an A

What is your numeric grade? 72

You will get a C

What is your numeric grade? 50

You will get an F

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Activity

import os

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numeric_grade = input('What is your numeric grade? ')

if numeric_grade.isnumeric() == False:

print('Enter a different value next time. Exiting.')

os._exit(0)

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numeric_grade = int(numeric_grade)

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# Write your code as if it would go here

if numeric_grade >= 60:

if numeric_grade >= 70:

if numeric_grade >= 80:

if numeric_grade >= 90:

print('You will get an A')

os._exit(0)

print('You will get a B')

os._exit(0)

print('You will get a C')

os._exit(0)

print('You will get a D')

os._exit(0)

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print('You will get an F')

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if numeric_grade >= 90:

print ('You will get an A')

if numeric_grade >= 80:

print ('You will get a B')

if numeric_grade >= 70:

print ('You will get a C')

if numeric_grade >= 60:

print ('You will get a D')

if numeric_grade < 60:

print ('You will get an F')

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if numeric_grade >= 90:

print ('You will get an A')

elif numeric_grade >= 80:

print ('You will get a B')

elif numeric_grade >= 70:

print ('You will get a C')

elif numeric_grade >= 60:

print ('You will get a D')

elif numeric_grade < 60:

print ('You will get an F')

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if numeric_grade >= 90:

print ('You will get an A')

elif numeric_grade >= 80:

print ('You will get a B')

elif numeric_grade >= 70:

print ('You will get a C')

elif numeric_grade >= 60:

print ('You will get a D')

else:

print ('You will get an F')

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What will it print?

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name = input('What is your name (lower case)? ')

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if name <= 'chase' or name > 'trevor':

print('name category 1')

elif name > 'chase' and name < 'ianto':

print('name category 2')

else:

print('name category 3')

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Activity

What will it print?

When the input is jeff ?

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name = input('What is your name (lower case)? ')

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if name <= 'chase' or name > 'trevor':

print('name category 1')

elif name > 'chase' and name < 'ianto':

print('name category 2')

else:

print('name category 3')

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Activity

What will it print?

When the input is chance ?

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name = input('What is your name (lower case)? ')

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if name <= 'chase' or name > 'trevor':

print('name category 1')

elif name > 'chase' and name < 'ianto':

print('name category 2')

else:

print('name category 3')

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Activity

What will it print?

When the input is iancu ?

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name = input('What is your name (lower case)? ')

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if name <= 'chase' or name > 'trevor':

print('name category 1')

elif name > 'chase' and name < 'ianto':

print('name category 2')

else:

print('name category 3')

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Activity

Blood Pressure

• Blood pressure measurement machines at pharmacies
• Some people don’t know how to properly interpret the numbers
• Might be good for machine to indicate low, normal, or high

Blood Pressure

• Systolic: Pressure on artery walls while ventricles in heart squeeze
• Diastolic: Pressure on artery walls while heart relaxes (thus, lower)

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• Write code that allows user to enter two inputs (systolic pressure and diastolic pressure) and determines if it is low, normal, or high

Activity

Is this correct?

systolic = float(input('Systolic pressure: '))

diastolic = float(input('Diastolic pressure: '))

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if systolic > 120:

if diastolic > 80:

print('High blood pressure')

elif systolic > 90:

if diastolic > 60:

print('Normal blood pressure')

else:

print('Low blood pressure')

Is this correct?

systolic = float(input('Systolic pressure: '))

diastolic = float(input('Diastolic pressure: '))

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if systolic > 120 and diastolic > 80:

print('High blood pressure')

if systolic > 90 and diastolic > 60:

print('Normal blood pressure')

if systolic > 0 and diastolic > 0:

print('Low blood pressure')

Is this correct?

systolic = float(input('Systolic pressure: '))

diastolic = float(input('Diastolic pressure: '))

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if systolic > 120 and diastolic > 80:

print('High blood pressure')

elif systolic > 90 and diastolic > 60:

print('Normal blood pressure')

else:

print('Low blood pressure')

Is this correct?

systolic = float(input('Systolic pressure: '))

diastolic = float(input('Diastolic pressure: '))

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if systolic > 120 or diastolic > 80:

print('High blood pressure')

elif systolic > 90 or diastolic > 60:

print('Normal blood pressure')

else:

print('Low blood pressure')