ME 4990: Intro to CS�Object-Oriented Programming & Machine Learning 101

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Functions

Outline

• Function
• Basics
• Practice

Function

• Learn python
• https://www.learnpython.org/en/Functions

Function

Function

• Equation of ellipse, is it a function for x(input)->y(output)?

Function

• A function is a package
• It is the basic element of modular design
• For each specific input, we can have only one output
• Which one is a function below?

Function in Python

• Infinite argument, infinite return

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Function

• Each argument can have a name
• When you call a function, you don’t� need to type in argument in order

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Function

• Argument type doesn’t matter, as long as they can be executed
• Strongly not recommend to use this property though

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Function

• Function arguments can have a default value
• Arguments with default value must be put at last

This is fine, arg1=“I say”

This is NOT fine, arguments with default value must be put at last

Best practice! Always specify argument name

Over-ride a default value

Function

• You turn!
• Test the argument settings of functions in python, do you find something new?

Function

• Argument can be function!

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Outline

• Function
• Basics
• Practice

Function

• Practice
• Write a Python function reverse(string_input) to reverse a string
• Sample input = “abcdefg”
• Sample output = “gfedcba”
• Cannot use python-default string reverse function

Hand-crafted functions

• First, def a function called distance_from_zero, with one argument (choose any argument name you like).
• If the type of the argument is either int or float, the function should return the absolute value of the function input.
• Otherwise, the function should return "Nope". Check if it works calling the function with -5.6 and "what?".
• (From https://erlerobotics.gitbooks.io/erle-robotics-learning-python-gitbook-free/content/functions/exercises_functions.html)

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Hand-crafted functions

• Calculate the surface area of a cylinder, the argument should include radius and height of a cylinder
• You need to use 3 functions:
• Area of the bases
• Area of the side
• Total area (called area) by merging the two, the function user should only use this function
• Enhancer:
• Set an argument called type in total area function with an additional argument called type
• Type can be ‘cone’ and ‘cylinder’, default cylinder
• Write additional code to calculate the area of a cone

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Programming with AI == Assemble Functions?

• Functions are the cells of program
• When you have a task, you shall think from top-down approach
• Any repetitive tasks that can be wrapped into functions?
• How can I structure the functions to achieve my goal?

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Program == a structure of functions

• Function is the cell of a program
• The Very Hungary caterpillar: https://youtu.be/75NQK-Sm1YY?si=GBcCGAZKQA8EXjIK
• Transcript here

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• How can we make a storyteller that generate the script with whatever fruits we have?
• For example, a mom wants to have the script: On Wednesday he eats three pineapples

My thoughts

• We have some sentences are unique
• We have some sentences are repetitive

Your Turn:

• Task: build a calorie tracking system to track how much weight do I gain each day
• What factors shall I consider for this task?
• What functions that reflect my understanding of these factors
• Something about eat?
• What food?
• The method of cooking? (Fried, boiled, etc.)
• Time of eating?
• Something about drink?
• Something about exercise?
• Anything else?
• Discuss the system with your neighbor, what factors to consider
• What functions do we need to reflect these factors
• How to structure the functions
• Ask ChatGPT to write the functions

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