Saving data with timestamps - Revision history

EdmondLascaris: /* Overview */

2022-01-18T22:07:51Z

Overview

← Older revision		Revision as of 22:07, 18 January 2022
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	* In python there is a special library called datetime that makes it easy to record and format dates and times.		* In python there is a special library called datetime that makes it easy to record and format dates and times.
	* In this lesson we will create a new program to get some experience with the datetime library before we add it back into our main program.		* In this lesson we will create a new program to get some experience with the datetime library before we add it back into our main program.


	== Learning Objectives ==		== Learning Objectives ==

EdmondLascaris at 05:26, 26 December 2021

2021-12-26T05:26:16Z

← Older revision		Revision as of 05:26, 26 December 2021
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	[[File:Screen Shot 2021-12-26 at 12.50.42 pm.png]]		[[File:Screen Shot 2021-12-26 at 12.50.42 pm.png]]

			* To list all the files present, enter '''ls'''
			* You should be able to see the '''data.txt''' file.

			[[File:Screen Shot 2021-12-26 at 4.24.31 pm.png]]

			* Finally, to read the data.txt file enter the command '''cat data.txt'''
			* This will output the complete listing of the file contents.

			[[File:Screen Shot 2021-12-26 at 4.25.33 pm.png]]

			* '''Congratulations!''' In our next lesson we will learn how to automate our python program so that we can collect data every hour.

EdmondLascaris at 01:51, 26 December 2021

2021-12-26T01:51:17Z

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	[[File:Screen Shot 2021-12-26 at 12.29.42 pm.png]]		[[File:Screen Shot 2021-12-26 at 12.29.42 pm.png]]

			* Right-mouse button click on the data.txt file and select '''Text Editor'''.
			* Alternatively, you can just double click on the '''data.txt file''' and it will open the default Text Editor.
			* The default Text Editor on the Raspberry Pi is '''Mousepad'''.

			[[File:Screen Shot 2021-12-26 at 12.43.28 pm.png]]

			* When the Text Editor opens you should be able to inspect your file.
			* The example below show that the new data added (always '''appended to the bottom''' of the file) includes the '''date and time'''.
			* If necessary, you can remove the other data entries that do not have a date and time.
			* Once you have finished editing your file '''Save''' the changes and '''Close''' the file.

			[[File:Screen Shot 2021-12-26 at 12.44.57 pm.png]]

			=== Verify data using the Terminal ===
			* Go to the top of the Raspberry Pi desktop and click on the Terminal icon.
			* The Terminal icon looks is a '''black box''' with a command prompt ('''>_''') inside.

			[[File:Screen Shot 2021-12-26 at 12.46.10 pm.png]]

			* This will open the '''Terminal''' window.
			* To verify where you are in the directory tree you can enter the command '''pwd'''
			* pwd is short for '''Present Working Directory'''.
			* In this case we are in the pi user home directory '''/home/pi'''

			[[File:Screen Shot 2021-12-26 at 12.47.19 pm.png]]

			* If ever you get lost and want to get back to the /home/pi directory enter the command '''cd ~'''
			* The ~ symbol is called '''tilde''', pronounced [TIL] + [DAH].

			[[File:Screen Shot 2021-12-26 at 12.48.30 pm.png]]

			* To look at the files and directories in the /home/pi directory enter the command '''ls'''
			* ls is short for '''List'''.

			[[File:Screen Shot 2021-12-26 at 12.49.39 pm.png]]

			* To enter the botanica-park-lake directory enter the command '''cd botanica-park-lake'''

			[[File:Screen Shot 2021-12-26 at 12.50.42 pm.png]]

EdmondLascaris at 01:30, 26 December 2021

2021-12-26T01:30:13Z

← Older revision		Revision as of 01:30, 26 December 2021
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	The path to this directory is '''/home/pi'''		The path to this directory is '''/home/pi'''
	Double click on your project directory. In this case it is '''botanica-park-lake'''		Double click on your project directory. In this case it is '''botanica-park-lake'''

			[[File:Screen Shot 2021-12-26 at 12.28.44 pm.png]]

			* This should then open the botanica-park-lake '''directory''' where all your project files are located.

			[[File:Screen Shot 2021-12-26 at 12.29.42 pm.png]]

EdmondLascaris at 01:24, 26 December 2021

2021-12-26T01:24:30Z

← Older revision		Revision as of 01:24, 26 December 2021
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	[[File:Screen Shot 2021-12-26 at 12.16.00 pm.png]]		[[File:Screen Shot 2021-12-26 at 12.16.00 pm.png]]

			* '''Paste''' these two lines of code into the atm_sensor_get.py program, just below the import datetime statement.

			[[File:Screen Shot 2021-12-26 at 12.18.37 pm.png]]

			* Within the '''atm_sensor_get.py''' program go down to almost the bottom of the code and '''edit''' the lines to reflect the example included below.
			* The key changes are highlighted in yellow:
			** '''print(“Date_stamp, .....“)'''
			** '''data = date_stamp + “,” + .........'''

			[[File:Screen Shot 2021-12-26 at 12.20.15 pm.png]]

			* If you '''Save''' and '''Run''' the program you should see the following output.

			[[File:Screen Shot 2021-12-26 at 12.21.36 pm.png]]

			* In the activity that follows we will check to see that the data has been saved correctly.

			== Verifying that data has been saved correctly ==
			* Our program saves data to the data.txt file in our project’s directory.
			* We need to check that the data has been saved correctly.
			* In this example we will use two techniques to verify that the data has been saved.
			* One method is to use the '''File Manager''' and the other method is to use the '''Terminal'''.

			=== Verify data using the File Manager ===
			* Go to the top left of the Raspberry Pi Desktop and click on the '''File Manager''' icon.
			* The File Manager icon looks like two yellow manilla folders.

			[[File:Screen Shot 2021-12-26 at 12.23.31 pm.png]]

			* The File Manager opens up to the pi user '''home directory'''.
			The path to this directory is '''/home/pi'''
			Double click on your project directory. In this case it is '''botanica-park-lake'''

EdmondLascaris at 01:16, 26 December 2021

2021-12-26T01:16:32Z

← Older revision		Revision as of 01:16, 26 December 2021
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	[[File:Screen Shot 2021-12-26 at 6.48.40 am.png]]		[[File:Screen Shot 2021-12-26 at 6.48.40 am.png]]

			* Add the day of the month ('''%d''').
			* The reason we have used this date format separated by '''hyphens (-)''', is because this style can be universally read by other python programs.
			* In the future we will write a program that will use the data to plot graphs.

			[[File:Screen Shot 2021-12-26 at 12.08.07 pm.png]]

			* We are interested in capturing data once every hour, so it makes sense to also record the hour and minute that the data was collected.
			* Update your code with the example below with the Hour ('''%H''') and Minute ('''%M''') Directives.
			* We have used the standard human readable format for '''Hour''' and '''Minute''', separated by a colon (''':''') – e.g. 16:24

			[[File:Screen Shot 2021-12-26 at 12.09.56 pm.png]]

			* Using the '''strftime()''' method we can now obtain an output ('''date_stamp''' variable) that has the date and time formatted correctly for other programs to use.

			[[File:Screen Shot 2021-12-26 at 12.11.05 pm.png]]

			== Updating our main program ==
			* When developing a large program, it is easier to break the key functions into separate modules so that they can be tested independently.
			* Once they are ready, they can then be merged into the main program.
			* We have created and tested our '''timestamp.py''' program and shown that it works.
			* In this example we will demonstrate how to copy sections of code into our original '''atm_sensor_get.py''' program to improve the functionality.

			=== Updating atm_sensor_get.py ===
			* Now that we have created our '''timestamp.py''' program and shown that it works, we can now copy sections of code into our original '''atm_sensor_get.py''' program
			* In the '''timestamp.py''' program copy the import datetime line by highlighting the code, '''right-mouse button click''' and selecting '''Copy'''.

			[[File:Screen Shot 2021-12-26 at 12.13.30 pm.png]]

			* In the '''atm_sensor_get.py''' program, paste the copied code by right-mouse button clicking and selecting '''Paste'''.
			* Add the code just below the '''import requests''' statement.
			* We try to keep imports together at the top of the code.
			* You should see the '''import datetime''' added to your code.

			[[File:Screen Shot 2021-12-26 at 12.15.02 pm.png]]

			* Go to the timestamp.py program and '''copy the two lines of code''' highlighted below.
			* You may need to '''delete''' some print statements that are not longer needed.

			[[File:Screen Shot 2021-12-26 at 12.16.00 pm.png]]

EdmondLascaris at 19:49, 25 December 2021

2021-12-25T19:49:16Z

← Older revision		Revision as of 19:49, 25 December 2021
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	=== Create a new file named timestamp.py ===		=== Create a new file named timestamp.py ===
	* From the Raspberry Pi main menu drop down select '''Programming > Python3 (IDLE)'''.		* From the Raspberry Pi main menu drop down select '''Programming > Python3 (IDLE)'''.

			[[File:Screen Shot 2021-12-26 at 6.34.54 am.png]]

			* This will open the Python Shell.

			[[File:Screen Shot 2021-12-26 at 6.35.47 am.png]]

			* From the '''File drop down menu''' select '''New File'''.
			* Add a comment to the new file - '''# timestamp.py'''.
			* The file name will be '''timestamp.py'''

			[[File:Screen Shot 2021-12-26 at 6.36.57 am.png]]

			* From the File dropdown menu select '''Save As'''.
			* Navigate to your project directory.
			* In this case it is '''botanica-park-lake'''
			* Name the file '''timestamp.py''' and click '''Save'''.

			[[File:Screen Shot 2021-12-26 at 6.38.07 am.png]]

			* Enter the following code:
			** '''import datetime''' – library import
			** '''now = datetime.datetime(now)''' – creates a new datetime object named now
			** '''print(now)''' – printing the now object
			* '''Save''' and '''Run''' the program

			[[File:Screen Shot 2021-12-26 at 6.39.45 am.png]]

			* The output in the Shell should show the year, month, day, hour, minute, second and microsecond time components.

			[[File:Screen Shot 2021-12-26 at 6.41.33 am.png]]

			=== Using the strftime() method ===
			* When we create a '''datetime object''' (now) we have access to a method for formatting output of the date object into more readable strings.
			* The method that does this is '''strftime()'''.
			* To format the datetime object we need to use some special characters called Directives.
			* Each Directive has a percentage sign ('''%''') and a single upper or lower-case letter ('''a-z, A-Z''').
			** '''%Y''' – full version of year – e.g. 2021
			** '''%b''' – month name short version – e.g. Jan, Feb, Mar
			** '''%d''' – day of the month 01 to 31 – e.g. 28
			** '''%H''' – hour 00 to 24 – e.g. 08
			** '''%M''' – minute 00 to 59 – e.g. 48
			* To use these Directives to format the date object add the following two lines of code.
			** '''date_stamp = now.strftime(“%Y”)'''
			** '''print(date_stamp)'''
			* The full code is included below.

			[[File:Screen Shot 2021-12-26 at 6.44.20 am.png]]

			* Save and Run the program.
			* There are two lines of output:
			** '''2021-05026 03:45:43...''' – print out of the '''now instance''' of the datetime object
			** '''2021''' – print out of the now datetime object formatted using the '''strftime()''' method to show the Year ('''%Y''').

			[[File:Screen Shot 2021-12-26 at 6.46.09 am.png]]

			* We can now keep on adding Directives to achieve our own customised format for the date and time.
			* In this example we have added the '''short version of the month''' using the ('''%b''') Directive – e.g. Jan.
			* To add the full version of the month we would use the ('''%B''') Directive – e.g. January.
			* To represent months as numbers 01 to 12 use the ('''%m''') Directive – e.g. 01 (for January).

			[[File:Screen Shot 2021-12-26 at 6.47.50 am.png]]

			* Save and Run the program and test some options.

			[[File:Screen Shot 2021-12-26 at 6.48.40 am.png]]

EdmondLascaris: /* Learning Objectives */

2021-12-25T19:34:39Z

Learning Objectives

← Older revision		Revision as of 19:34, 25 December 2021
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	== Learning Objectives ==		== Learning Objectives ==
	Learn how use the python datetime library.		* Learn how use the python datetime library.
	Learn how to update our main program with the datetime library functions.		* Learn how to update our main program with the datetime library functions.
	Learn how to verify that our data has saved correctly using the File Manager and Terminal.		* Learn how to verify that our data has saved correctly using the File Manager and Terminal.


			== Getting the current date and time ==
			* In this example we will experiment with a new python library named datetime.
			* We will demonstrate how to get the current computer time, and also learn how to format the response.
			* More information on formatting the datetime output can also be obtained from W3Schools at the following URL: Python Dates (w3schools.com)

			=== Create a new file named timestamp.py ===
			* From the Raspberry Pi main menu drop down select '''Programming > Python3 (IDLE)'''.

EdmondLascaris: Created page with "== Overview == * In this lesson we are going to learn how to add a date and time to our data which is sometimes called a timestamp. * A timestamp records the current time tha..."

2021-12-25T19:32:30Z

Created page with "== Overview == * In this lesson we are going to learn how to add a date and time to our data which is sometimes called a timestamp. * A timestamp records the current time tha..."

New page

== Overview ==
* In this lesson we are going to learn how to add a date and time to our data which is sometimes called a timestamp.
* A timestamp records the current time that an event took place.
* This becomes important later when we want to graph the data that we collected.
* Computer settings are important with dates and times.
* When we initially set up our Raspberry Pi, we need to define localisation options to be Melbourne, Australia.
* The computer can then calculate our local time and even make allowances for daylight savings and atomic clock corrections.
* It is also important that the Raspberry Pi is connected to the internet so that it can re-calibrate the onboard clock.
* In python there is a special library called datetime that makes it easy to record and format dates and times.
* In this lesson we will create a new program to get some experience with the datetime library before we add it back into our main program.

== Learning Objectives ==
Learn how use the python datetime library.
Learn how to update our main program with the datetime library functions.
Learn how to verify that our data has saved correctly using the File Manager and Terminal.