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Announcements
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Welcome party
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HW1 due, HW2 and partners posted
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Questions
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Practice: function to convert miles to kilometers
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1.61 km per mile
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Problem: what icon to display in weather app?
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Simplified problem: difference between current and “hot” temperature (i.e., should the app show the current temperature in red)
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Decision time
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we can do this with Python’s if
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anatomy of if
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if <condition>:
<indented lines only executed when condition is True>
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need to make program behavior conditional on state of the world
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diagram possible states and actions
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let’s say text has more than two settings (yellow, orange, red)
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if/elif/else nice way to structure this decision
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Practice: number guessing game
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given a player’s guess and a secret number, print “cold” “warm” or “lava”
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only print one hint
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boolean expressions
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relational operators
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less than (<), less than or equal to (<=)
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greater than (>), greater than or equal to (>=)
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equal (==)
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not equal (!=)
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can use and, or to combine expressions
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check if variable x is positive number at most 10: x > 0 and x <= 10
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can use parentheses to control evaluation
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current_temp > hot_temp and chance_of_rain > 0.4 or chance_of_clouds > 0.5
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(current_temp > hot_temp and chance_of_rain > 0.4) or chance_of_clouds > 0.5
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same as first version, by default ands and ors are evaluated left to right
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current_temp > hot_temp and (chance_of_rain > 0.4 or chance_of_clouds > 0.5)
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Practice: write an absolute value function
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Let’s imagine our guessing game is played over many rounds
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We might copy and paste the code for each round with minor changes
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Is this a place where a function would be useful?
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What part of the code should be moved into a function and what would it look like?
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Partner activity
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Here is a common interview question in CS.
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Write a program called fizzbuzz.py that asks the user to input a number num and outputs the following.
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Outputs “fizz” if num is divisible by 3,
Outputs “buzz” if num is divisible by 5,
Outputs “fizzbuzz” if num is divisible by both 3 and 5, and
Outputs num otherwise.
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Modify your program so that it also outputs “jazz” if num is divisible by 7. Note that it should also output “fizzjazz” if it is divisible by 3 and 7, and so on for all other combinations above
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