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Basic Function

A function performs a per-defined task when you use it (also known as “when you call it”).

Now, we can only use functions that are pre-defined by python. In the Advanced Function handout, we will learn how to define a function by ourselves.

Here’s the full process of using a function:

function_diagram

Basic Structure

function_basic_structure

Parameter(s)

This is the place where you give data to the function.

You can don’t give a function any parameter, one parameter or multiple parameters. Parameters are separated by commas.

For example: (The following code is just for demonstrate how to give data to a function, it can’t actually run because those functions are not defined yet.)

Return Value

This is how you get new data from the function.

A function can return no value or one value. You can assign the value returned from a function to a variable.

For example: (The following code is just for demonstrate how to get value returned from a function, it can’t actually run because those functions are not defined yet.)

How to Describe a Function

Knowing how to describe a function is very important when you are trying to figure out how to use a function.

  1. Signature

    Signature of the function is the function name and the parameter it takes. For example, the signature of the print function is print (data)

  2. Parameters

    Explain what does each parameter means. For example, data parameter means the data print function will show in the shell.

  3. Return value

    Describe what and how many value the function will return. For print function, it returns no value.

  • Usage: output a value

  • Signature: print (data)

  • Parameters:

    Name Value Type Meaning
    data any type The data will show in the shell

  • Return value: None

str Function

  • Usage: convert a number type value to string type value

  • Signature: str (number)

  • Parameters:

    Name Value Type Meaning
    number Number The number you want to convert to string

  • Return value: same number, but is in string type.

Last update: March 24, 2021
Created: March 24, 2021