3.2.1

Data Flow

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Passing Parameters

Passing parameters allows us to send data into a subroutine.

Passing parameters

Passing parameters

  • Passing parameters is the process of passing a piece of data into a subroutine.
  • The data is then assigned into a local variable (parameter) inside of the subroutine.
  • We can then use this data inside the subroutine.
Parameters vs global variables

Parameters vs global variables

  • We could also pass data by putting it inside of a global variable.
  • This is considered bad practice, since it can be accessed by any subroutine. Passing parameters is a much more secure, and maintainable approach.

Returning Multiple Values

Sometimes a situation might arise where we wish to return multiple pieces of data from the same subroutine.

Returning values

Returning values

  • Functions are subroutines that return a value.
  • Functions are limited to returning a single value, which is sometimes problematic.
Returning a list

Returning a list

  • One solution to this problem is to use a list of values.
  • We can create a list, and append each value we want to return.
  • This list can then be returned, containing all of the values.
Restructuring subroutines

Restructuring subroutines

  • In other scenarios, it can be a much better idea to restructure subroutines to return only a single value.
  • Often, multiple return values is a sign of poor program design.
Jump to other topics
1

Introduction to Python

1.1

Python

1.1.1Python
1.2

Input & Output

1.2.1Input & Output
1.3

Data Types

1.3.1Data Types
1.4

Variables & Constants

1.4.1Variables & Constants
1.5

Operators

1.5.1Arithmetic & Relational Operators1.5.2Boolean & Assignment Operators 2
1.6

Program Flow

1.6.1Selection1.6.2Iteration
2

Data Structures

2.1

Lists & Strings

2.1.1Lists2.1.2Strings
2.2

File Handling

2.2.1File Handling
3

Modularity

3.1

Subroutines

3.1.1Subroutines
3.2

Data Flow

3.2.1Data Flow
4

Good Practice

4.1

Naming & Whitespace

4.1.1Identifiers4.1.2Whitespace
4.2

Comments

4.2.1Comments
4.3

Exceptions

4.3.1Exceptions

Practice questions on Data Flow

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  1. 1
    Ways of passing data into a subroutine:Fill in the list
  2. 2
    When data is passed as a parameter, it is assigned to what type of variable inside the subroutine?Multiple choice
  3. 3
    Methods of returning multiple values:Fill in the list
  4. 4
    Returning multiple items using a list:Put in order
  5. 5
    Which, in most situations, is the best method to use when multiple return values are required?Multiple choice
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Subroutines

Identifiers