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Variables, expressions and statements: user input

Learning objectives

  • Practice using the UPPMAX documentation
  • Practice using the Python book How to Think Like a Computer Scientist: Learning with Python 3
  • Get the type of an object
  • Create a variable
  • Use a variable
  • Practice converting an equation to Python code
  • Find and use the operator for exponentiation
  • Practice the modulo operator
  • Practice converting a simple text question to Python code
  • Learn how to ask a user for input
  • Use input in a calculation
For teachers

Teaching goals are:

  • Learners have worked with variables
  • Learners understand the purpose of variables
  • Learners have obtained the data type of a variable
  • Learners have heard about what a data type is
  • Learners have practiced convert an equation and a text question to Python
  • Learners have read on operators
  • Learners have worked with the modulo operator
  • Learners have written code that asked for user input

Lesson plan:

  • 5 mins: prior knowledge
  • 5 mins: presentation
  • 15 mins: challenge
  • 5 mins: feedback

Prior questions:

  • What do we mean with user input?
  • In which ways can we get user input?
  • Why would you want to use user input in your program?

Overview

In any non-trivial calculation, we want to let our computer remember things, such as the content of a data file, or the parameters/settings we use in our program. Variables allows one to make a computer store ('remember') information. Here we use our first simple variables.

Also we practice converting an equation and a mathematical problem to Python code. We will discover the helpful modulo operator.

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    python[[Python]]

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      interpreted_language[Interpreted language]
      programming_language[Programming language]
      scripting_language[Scripting language]
      interpreter[Interpreter]
      scripts[Scripts]
      text_files[Text files]
    end
    style sub_programming_language fill:#ccf,color:#000,stroke:#fcc

    subgraph sub_programming_terms[Programming terms]
      user_input[User input]
      %% file_io[File I/O]
      %% command_line_arguments[Command-line arguments]
      variables[Variables]
      operators[Operators]
      %% functions[Functions]
      python_packages[Python packages]
      %% graphics[Graphics]
    end 
    style sub_programming_terms fill:#cfc,color:#000,stroke:#fcc

    subgraph sub_uppmax[UPPMAX]
      uppmax[UPPMAX]
      uppmax_modules[UPPMAX modules]
      uppmax_clusters[UPPMAX clusters]
      text_editors[Text editors]
      x_forwarding[X-forwarding]
      remote_desktop[Remote desktop]
    end
    style sub_uppmax fill:#fcc,color:#000,stroke:#fcc

    python --> |is a| programming_language
    python --> |is a| interpreted_language
    python --> |is a| scripting_language

    programming_language --> |uses| text_files
    interpreted_language --> |has a| interpreter
    scripting_language --> |is|interpreted_language
    scripting_language --> |runs| scripts
    scripts --> |are| text_files
    %% scripts --> |can use| command_line_arguments

    python --> |has| python_packages
    python --> |has| variables
    %%python --> |has| functions
    python --> |has| operators
    %%functions --> |use| variables
    operators --> |work on| variables
    %%python_packages --> |allow| graphics
    python_packages --> |allow to use| user_input
    %% python_packages --> |allow to do| file_io
    %% python_packages --> |allow to use| command_line_arguments

    uppmax --> |has| uppmax_clusters
    uppmax_clusters --> |have| uppmax_modules
    uppmax_clusters --> |have| text_editors
    uppmax_clusters --> |allow| x_forwarding
    uppmax_clusters --> |has| remote_desktop
    uppmax_modules --> |allow the use of| python_packages
    uppmax_modules --> |allow the use of| interpreter

    text_editors --> |work on|text_files
    %%x_forwarding --> |allows|graphics
    %%remote_desktop --> |allows|graphics


    variables ~~~ uppmax

Exercises

See the exercise procedure here.

Exercise 1: input

Learning objectives

  • learn how to ask a user for input
  • use input in a calculation

Read the following section of How to Think Like a Computer Scientist: Learning with Python 3:

  • 2.10. Input

Then in section 2.14, do exercise 8.

2.14.8

Write a Python program to solve the general version of the above problem. Ask the user for the time now (in hours), and ask for the number of hours to wait. Your program should output what the time will be on the clock when the alarm goes off.

Answer

Here is a possible implementation:

t_now = int(input("Enter the current hour"))
n_hours = int(input("Enter the number of hours"))
t_future = (t_now + n_hours) % 24
print("Time after that number of hours:")
print(t_future)