Class 19 – Friday October 11

Decisions made easy

I am positive — My favorite color is hue — Easy decision

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Look both ways

• Back or ahead

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Agenda

• Gain an understanding of the Python relational and logical operators

• Introduce the if statement

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Problems

• Program can_you_relate.py

• Program logical_operators.py

• Program acid_test.py

• Program what_color_will_my_chrysanthemums_be.py

• Program robotomy.py

• Program daisy_daisy.py

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To do list

• Really examine the artifacts

• Read epistle on decision making

• Do homework 17 and 18

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Expanded problem solving

• Some problem solving requires the ability to react — depending upon the circumstances different conditions need actions to be performed. Python provides the if statement for decision making.

• The if statement uses logical test expressions to determine which action to perform.

• There are variants of the if statement to make decisions based on one, two, or several possibilities.

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Riddle me this — what classrooms are viable for scheduling CS 1112

• The School of Engineering and Applied Science (SEAS) has four-tiered classrooms: MEC 205, Olsson Hall 120, Rice 130, and Thornton E316. All four rooms provide WIFI access. Only MEC 205, Olsson Hall 120, and Rice 130 support classroom sizes greater than 100. MEC 205 and Olsson 120 do not provide student power ports.

• The registrar has rules about scheduling 75-minute classes. They can meet anytime on Tuesdays or Thursdays. On Mondays, Wednesdays, or Fridays they cannot be scheduled before 2:00 PM.

• Surveys indicate that on average, students preferred classes whose starting times do not occur before 10:00 AM or after 2:00 PM.

• Tiered seating allows for a better eye contact between an instructor and other members of the class. Better eye contact encourages student engagement.

• Jim Cohoon has several general teaching preferences.

• Maximize student access to his courses.

• Class sessions be 75-minutes.

• 1xxx and 2xxx level courses meet three times a week.

• 3xxx and 4xxx courses meet twice a week.

• Classrooms should provide student access to WIFI and to power ports.

• Maximize student engagement.

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Being logical

• Program can_you_relate.py

• Introduces the comparison operators

Three program runs

Enter number: 12

Enter number: 11

12 < 11 : False

12 > 11 : True

12 <= 11 : False

12 >= 11 : True

12 == 11 : False

12 != 11 : True

Enter number: 3

Enter number: 14

3 < 14 : True

3 > 14 : False

3 <= 14 : True

3 >= 14 : False

3 == 14 : False

3 != 14 : True

Enter number: 7

Enter number: 7

7 < 7 : False

7 > 7 : False

7 <= 7 : True

7 >= 7 : True

7 == 7 : True

7 != 7 : False

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• Program logical_operators.py

• Introduces the logical operators

Program run

#### Logical values (bool)

True

False

##### Logical and

True and True = True

True and False = False

False and True = False

False and False = False

##### Logical or

True or True = True

True or False = True

False or True = True

False or False = False

##### Logical negation

not True = False

not False = True

##### Logical includes

1 in [3, 1, 4, 1, 5] = True

2 in [3, 1, 4, 1, 5] = False

##### Logical exclusion

1 not in [3, 1, 4, 1, 5] = False

2 not in [3, 1, 4, 1, 5] = True

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Building a better chrysanthemum

• Program acid_test.py

• Determine whether its input pH level is acidic; i.e., less than 7.0

Three program runs

Enter pH level: 6.5

True

Enter pH level: 7.0

False

Enter pH level: 7.5

False

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• Program what_color_will_my_chrysanthemums_be.py

• Determine chrysanthemum color given an input soil pH level, where acidic soil produces pink chrysanthemums and non-acidic soil produces blue chrysanthemums.

Three program runs

Enter soil pH level: 6.5

pink

Enter soil pH level: 7

blue

Enter soil pH level: 7.5

blue

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Program daisy_daisy.py

• Report message based on indicated day of week. The message should be weekend day for Sunday and for Saturday, the message should be 'start of school week' for Monday, the message should be 'end of school week' for Friday, and 'school day', otherwise.

Seven program runs

Enter day of week: Sunday

weekend day

Enter day of week: monday

start of school week

Enter day of week: TUESDAY

school day

Enter day of week: Wednesday

school day

Enter day of week: Thursday

school day

Enter day of week: Friday

end of school week

Enter day of week: Saturday

weekend day

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Program robotomy.py

• Determine what happens when a robot comes knocking on a door.

• If the door is locked, the robot should be instructed to turn around.

• If the door is instead unlocked, the robot should be instructed to open the door and enter the room. Before entering, the robot should determine whether the light is off. If it is off, the robot should be instructed to first turn on the light.

• Observation there is one procedure to perform if the door is locked, another to perform if it is unlocked. The procedure to perform if the door is unlocked, requires analysis whether the light is on.

Three program runs

class="coding">

Door (locked / unlocked): locked

Turn around

class="coding">

Door (locked / unlocked): Unlocked

Open the door

Light (on / off): on

Enter the room

Door (locked / unlocked): unlocked

Open the door

Light (on / off): Off

Turn on the light

Enter the room

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© 2019 Jim Cohoon

Resources from previous semesters are available.