SENG 208 Week -5 Python Functions Presentation
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- 2. FUNCTION BASICS A functionis a block of code that performs a sequence of instructions.
- 3. FUNCTION BASICS A functionis a block of code that performs a sequence of instructions. Whenever the function is “called”, the sequence of instructions is executed.
- 4. FUNCTION BASICS Functions cantake inputs and return outputs based on those inputs. Here are examples of built-in functions you might have seen:
- 5. FUNCTION BASICS • Somefunctions perform actions instead of returning outputs. • These actions are called side effects. For example, displaying text in the interactive console is a side effect of the print.
- 6. FUNCTION BASICS • Thetext outputs in the console are examples of a side effect. There is no value that is produced by calling print()
- 7. FUNCTION BASICS Function diagramssummarise what functions do
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- 9. Anatomy of aUser-defined Function
- 10. Parameters and Arguments •A parameter is a variable used in the definition of a function, which will be initialised with an argument value during a function call. • The particular name we use for a parameter is irrelevant as long as we use the name consistently in the function definition.
- 11. Parameters and Arguments •Syntax of creating a function:
- 12. Parameters and Arguments •Syntax of creating a function:
- 13. Unindented function body •Python is unusual among programming languages in that it uses indentation to determine what’s in the body of a function.
- 14. Python Function CallModel
- 15. Multiple parameters A functioncan take as many parameters as needed. They are separated via comma.
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- 17. Functions calling functions Thefunction hypotenuse calls the square function we just defined.
- 18. Functions calling functions Thefunction distanceBetweenPoints calls the hypotenuse function defined above.
- 19. Creating a functionwithout any parameters The function hypotenuse calls the square function we just defined.
- 20. Local variables • Anassignment to a variable within a function definition creates/changes a local variable. • Local variables exist only within a function’s body. They cannot be referred outside of it. • Parameters are also local variables that are assigned a value when the function is invoked. They also cannot be referred to outside the function.
- 21. RETURN VS. PRINT •return specifies the result of the function invocation • print causes characters to be displayed in the shell (side effect).
- 22. RETURN VS. PRINT •Don’t confuse return with print!
- 23. Incremental Development ofYour Code • When writing your own functions or any other type of code, do not attempt to write it all at once! • Try to complete small tasks one at a time and test along the way. • Store longer expressions in variables as you go along, and continue to reference those variables.
- 24. Incremental Development ofYour Code
- 25. Visualizing Code Executionwith the Python Tutor • Python Tutor: http://www.pythontutor.com/visualize.html
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