macOS, Visual Studio Code, Python 3.7.5, OpenCV4

It took a few attempts to get a compatible Python and OpenCV library running under Visual Studio Code on macOS Catalina using a virtual environment. I made a video to show how I got this going – this post just adds some more details.

There is also an excellent tutorial from Microsoft:

Getting Started with Python in VS Code

Note: virtual machine rendering problem

Visual Studio Code running on a virtual machine may have problems rendering the interface. This seems to be related to the underlying Electron framework and GPU acceleration. I made a quick video to show how I got around this:

Fix rendering problems for Visual Studio Code running on a virtual machine

Install Python 3.7.5

A virgin Mac comes with Python 2.7 installed – this is not recommended and V3.7.5 works with OpenCV4 on a Mac. V3.8 does not work at the time of writing (although since I started writing this post it looks like it now does). Download the installer from the main python website by selecting Downloads, Mac OS X, and then selecting the 64-bit installer:

Run the installer – I used all default settings.

Install Visual Studio Code

Download the installer from Visual Studio Code and immediately move the downloaded file to the Applications folder. (This is the actual application, not an installer). Try to run once – macOS will refuse due to security:

Close the message, open System Preferences, and select the Security and Privacy settings. Then select “Open Anyway” to allow VSC.

Visual Studio Code should now start:

Configure Python

Open a folder by selecting Open folder and then add a new file. Save the file using the .py extension:

Visual Studio Code immediately offers to install the Python extension, select Install:

On a virgin Mac there will now be a prompt to install command line developer tools, so click Install if prompted and allow the installation to complete before returning to Visual Studio Code.

The status bar will show the selected interpret if everything has gone well:

Install the linter (pylint): this helps analyse the code for bugs and style issues. It also might not work first time but we can fix shortly…

If the terminal window suggests upgrading pip, the Python package manager, then go for it by running the following in the terminal window:

python3 -m pip install --upgrade pip

Make a virtual environment

A virtual environment is a self-contained directory tree that contains a Python installation for a particular version of Python

https://docs.python.org/3/tutorial/venv.html

Each project can use its own virtual environment to ensure any modules it requires don’t clash with modules in other projects.

From the terminal create a virtual environment:

python3 -m venv .venv

Visual Studio Code will detect this new environment and offer to select it for the current project folder – select Yes:

Because this is a new Python environment you may need to install the linter again:

Now – the bit that confused me… the project is now using the .venv virtual environment:

However, the terminal session has so far only created the environment, it has not activated it for itself. The shell identifier says:

jon@Jons-MacBook-Pro Python %

There are two ways to fix this. First, using the source command in the terminal window:

source .venv/bin/activate

Second, by creating a new Terminal session using the command palette. (Select View, ten Command Palette):

Now the terminal shows that it’s using the virtual environment:

Install OpenCV

At last we can install OpenCV. Using the terminal session in the virtual environment we can first search for OpenCV packages:

python3 -m pip search opencv  

When called with -m module-name, the given module is located on the Python module path and executed as a script

https://docs.python.org/3/using/cmdline.html

We see results like this:

opencv-utils (0.0.2) – OpenCV Utilities
ctypes-opencv (0.8.0) – ctypes-opencv – A Python wrapper for OpenCV using ctypes
opencv-wrapper (0.2.3) – A Python wrapper for OpenCV.
opencv-cython (0.4) – An alternative OpenCV wrapper
dajngo-opencv (0.3) – Django Opencv integratio
opencv-python (4.1.2.30) – Wrapper package for OpenCV python bindings

For this test I’m using opencv-python. The details on version 4.1.2.30 can be found on the Python Package Index site. Interestingly this version was only released a few hours ago and says it supports Python 3.8 😬 I guess I’ll try this on a virtual machine first to check it’s all ok!

Install OpenCV using pip:

python3 -m pip install opencv-python

Write some code and fix the linter

First test: import the OpenCV module and print the library version.

import cv2
print('Using OpenCV version {0}'.format(cv2.__version__))

After running this output is shown in the terminal:

But – there’s a problem. In the editor the linter is suggesting that cv2 is not a known module:

This has been seen before on the pylint GitHub issues page. For me, the solution is to edit the .vscode settings. Using ⇧⌘E (shift+command+E) to view the explorer page, expand the .vscode file and click settings.json:

Add a comma to the end of the line of the existing setting, then add the following new setting:

"python.linting.pylintArgs": ["--generate-members"]

My settings now look like this:

And now the red squiggle has gone from cv2.__version__ 😀

All that remains is to learn Python and OpenCV which will surely lead to great things!

Hope this helps.

Apple’s best hidden Trackpad gesture!

Apple trackpads, both external and built-in, have one fantastic gesture which is not enabled by default:

3 finger drag

https://support.apple.com/en-us/HT204609

This allows you to easily grab windows and files without needing to hold down the trackpad like a mouse button. For GUI designers it means quickly resizing and positioning controls, like Tom Cruise in Minority Report 😎

3 useful keyboard mods for better editor support on Windows 10 using Parallels

Tested with Parallels Desktop 15 Pro Edition on macOS Catalina.

Problem 1: using Visual Studio or notepad++ or any similar multi-document application in Windows 10 on a Mac using Parallels, ⌘W (Command+W) maps to Alt+F4. This means To close just an editor page you have to revert to the original Windows shortcut of Control+F4 which is a minor pain on a Mac with the Touch Bar instead of function keys.

Solution 1: change the Parallels preferences to remap ⌘W to Ctrl+F4. ⌘Q will still close an application but ⌘W will now close an internal editor window; this is the same behaviour used in Safari to close the whole application (⌘Q) or close just one page (⌘W).

Problem 2: Control+Tab and Shift+Control+Tab don’t switch between editor windows.

Solution 2: a recent update to Parallels resulted in these shortcuts being used for Parallels tab switching. They don’t get passed on to the VM. Just unchecking these shortcuts fixes the problem.

Apple Trackpad on Windows with 3-finger drag!

A month ago, when I needed to get a new laptop for work, I switched from a MacBook Pro to a Dell XPS 9750, saving £100’s of pounds for what on paper is an almost identical laptop. Except it isn’t. Dell’s XPS is astonishingly good, and it’s a priviledge to own one, but I’ve become an Apple devotee over the years and can’t change it. My days are spent programming for Windows so I need a fast PC development environment and therefore the XPS makes sense. With the MBP I need to use VMWare Fusion or Parallels, and Apple are really pushing my (and other people’s) limits by charging so much money for memory and SSD upgrades. So I went for the XPS. 

Of all the little things I miss, 3 finger dragging is way up there. To be fair, the XPS’s trackpad is one of the best out there for Windows laptops, and with Windows 10 there is a double-tap to drag gesture which is fantastic. But the trackpad is too small and two taps (versus a single 3-finger drag) are one tap too many.

After a bit of Googling, I found Magic Utilities, a company that make drivers and utilities for Apple wireless keyboards, the magic mouse, and the Magic Trackpad. When I used Windows as a virtual machine on the MBP I got used to a particular mapping of the Alt and Cmd keys; the keyboard utility app lets me restore these mapping. Also, I’ve just discovered that the Eject key now becomes delete, although my fingers have 5 years of muscle memory which means that delete = Function + Backspace.

(Now, with the Apple keyboard, the function and control keys are where they should be IMO! There are loads of people asking Dell whether it’s possible to swap these keys on the Dell keyboards but it really can’t be done.)

Apple’s wireless Magic Trackpad performs terribly on Windows 10 by default. There are few (if any) gestures, and the whole feel of the cursor on the screen is terrible. Magic Utilities Trackpad app changes this completely:

Now I can scroll, drag, single-finder tap, and not a mechanical click in sight. 

I’ve now bought a one year licence after trialling this for a couple of weeks without any problems. Now I work with the XPS lid closed and just the wireless mouse and keyboard in front of an external 4K monitor. 

For the odd occasional where I might work 12 hours a day the little things, both positive and negative, soon accumulate, so the ~£20 cost of this bundle is really a bargain. 

Now if I could just find a similar utility to turn Windows 10 into Mac OS… 😀

iOS mail signature woes

This morning I decided to update my company email signatures and synchronise them between the MacBook Pro (Mavericks), the iPhone and the iPad.

A couple of hours later I finally cracked it!

The main issue I had was preventing iOS from automatically converting numbers and addresses into links. This is a particular problem when it gets it wrong and doesn’t provide any obvious means of editing/cancelling the links.

First I used an online HTML editor to make my signature:

Online_HTML_Editor__Real_time_online_with_preview

Then I copied the rendered output to the mail app on Mavericks:

Signatures_and_Inbox

Then I tried emailing myself using the new signature. On Mavericks it looked perfect, but on the iPhone it misinterpreted some of the  information:

2014-01-21_10_22_14-3

In this case just the company number was displayed as a telephone number link. But on one of my other email accounts half of the address was converted to a link while the other half remained as text.

I don’t think it’s possible to suppress this automatic conversion, and I can live with it because usually it works quite well.

My iPhone and iPad problems started when I tried to copy the signature to the clipboard and paste it into the signature box on the settings app:
2014-01-21_10_30_19-3

So, the copy and paste has worked, but it’s not what I want. I’ve lost the font type and size, and nearly everything is blue.

I then tried using the online HTML editor on the iPhone but the rendered output had automatic link conversions on the telephone numbers. Not really a problem but it was still doing things I didn’t want.

Then I decided to try a cunning plan: I sent myself an email with the signature broken into multiple lines, so that no one line appeared to contain a useable telephone number or address:

2014-01-21_10_41_02-2

Then I copied the message to the iPhone’s email signature editor but it lost the font!

Finally, as I was considering giving up, I went back to the MacBook and pasted my signature onto Evernote and split it into multiple lines again. Back on the iPhone I copied the mangled signature  from Evernote to the signature editor:

2014-01-21_10_55_02-2

Progress! Next I edited the signature to remove the line breaks:

2014-01-21_10_58_05-2

And finally an email:

2014-01-21_10_58_44-2

Ok, so the telephone numbers have been converted into links but I suspect I can never prevent that, and since these are telephone numbers then I’m fine with it. But I’ve got my font type and size, and the company number is just a number (not a link), and I’ve roughly got what I wanted.

Then I repeated the last few steps again on the iPad.

There are plenty of iOS apps for making signatures but I really wanted to have the in-built signature working. And now I have it. But there must be a better way, either now or in the future. And once Apple and Google start talking to each other I might even see emails as they arrive without having to restart the mail app on Mavericks.

OS X, Python 3.3, LiClipse

Yesterday I tried to get Eclipse and PyDev installed on my MacBook Pro (running Mavericks). After a couple of hours of struggling I gave up and discovered LiClipse which is a highly recommended system for working with Python and many other languages from the Eclipse framework.

I used a clean OS X Mavericks virtual machine to get my installation nailed down, especially important since I wanted to work with Python 3.x.

Downloads

Download and install:

  1. Python 3.x.
  2. Java 7.
  3. LiClipse: click the Google Drive link, select the latest version (currently 0.9.6), click and download the OS X file (currently liclipse_0.9.6_macosx.cocoa.x86_64.dmg), then install using all default options.

Configuration

Eject all download package (DMG) folders on the desktop.

Use Finder and go to Applications, open the liclipse folder, then drag the LiClipse app to the dock.

Run LiClipse. If a software update prompt appears for Java SE 6 then install it.

Accept all defaults when starting for the first time and restart the app.
 
Select File / New project, then select PyDev/PyDev Project:
ad45e741fc7fadfa78252bb606d55228

Hit Next, then set a project name and click the link to configure an interpreter:

489ed184ec9e6e8b074feccf177fcb78

Select the advanced configuration option:

ff2c2bbde406a0db49eae0d0d91f25e7

Then select python3.3:

32ca7a2249fdaa5c7ab1905a39b37dbb

On the next screen make sure all folders are selected:

378876332975796581d1a1bba04b66ee

Back on the new project screen make any other changes – I opted not to configure the Python path – then click Finish:

04b122222be512f58fe0f7fa062a8801

The Open Associated Perspective prompt may appear – I chose to associate the project with the PyDev perspective:

0a8180c02287ff3b076f068ffd8b3004

These Python and perspective settings will be used the next time LiClipse is started for Python projects.

Quick Python test

Following on from the above new I added a new Python file, entered a couple of lines of code, and ran it:

5b8f1d79fa162facf4e384b1394d0a99

132a82e84ba8b7066edba59927094d74

4a997671f4a90eee79e6c84d6342f354

638b29041e54c6d81427455cf5407130

feb22a04d91362315bae7493317c90ec

Debugging

If the debugger is used, for example by stepping through the code, there’ll be an option to switch to another perspective – this should be used for debugging:

a8a26c331c032792e467e96787890a55

This presents more window areas for examining variables, viewing the editor and console output, etc:

a9b4613df5986bd7bd9915660c715f15

After the debugging session is complete the Debug perspective will still be active. To switch back to the original perspective use the menus:
  • Window | Open Perspective | Other, then select PyDev.

Standing desk (ikea hack)

I’m starting my third week of standing, rather than sitting, at work. There’s been much written on this subject and I’m not 100% sure that it’s the right long term solution but so far I feel more focussed and less like a 12-hour-a-day slob.

My office already had some Ikea Expedit shelves on the wall, and I’d tried converting my table into a simple standing desk. But the table was around 6 inches too low and due to it having just four very extended legs it was also quite wobbly.

2013-12-03 09.15.08

Then I saw this excellent Ikea Hack for an Expedit Standing Desk.

My hack is a variation on the above desk system; I strengthened the front 5*1 unit by retaining the first and last internal panels – this had the advantage of providing a bit more storage as well. The wall shelves came down and formed sides to the desk, and now it’s starting to feel pretty cool (this being day 2 of this configuration).

I modelled the system on Google Sketchup:

i1 i2 i3 i4

Then I built it, and here it is:

2013-12-16 18.37.43 2013-12-16 18.38.12

Once I can lose the bits and bobs on the floor and tidy up the shelves it’s going to be super cool.

OS X Pages 5.0 graphics in header

The latest version of Pages for OS X and iOS is great for iCloud users who want to edit documents on both desktop and mobile with maximum compatibility. But Pages for OS X has lost many features to attain this compatibility.

Yesterday I tried to create a new document with a company logo in the header, so that it would repeat on every page. The process wasn’t intuitive!

First off the Pages 5.0 manual is easiest to find via Pages, rather than Googling for it:

Fullscreen_01_11_2013_11_43-2

Then the trick is discovering master objects.

You can add text, watermarks, logos, or other images that appear in the same place in the background of every page of your document. These repeated elements are called master objects.

So here’s my sequence of events for getting an image into the document header so that it repeats on every page:

  1. New (blank) document.
  2. Turn on Layout View (⇧⌘L). This makes it a little easier to see where the header and body areas of the document are.
  3. Drag and drop the logo to the document body.
  4. Resize the logo and drag to the appropriate location in the header. Caution: if the resized logo fits within the header cell boundary it seems difficult or impossible to re-select it. I made mine slightly larger so that the mouse cursor could just click it.
  5. With the logo selected use the menu Arrange | Section Masters | Move Object to Section Master to make the logo a master object.
  6. If the logo needs to be repositioned use the Arrange | Section Masters | Make Master Objects Selectable to allow this and any other background objects to be selected.

Shapes for header/foot borders

This technique can also be used with shapes to allow the header and/or foot to have a full width border. For example, after setting up the header text try adding a simple shape to the document:

Untitled-2

Resize the shape and add any effects, move it below the header, use the menus again to make it a master object:

Untitled-2

When viewed as a PDF in Preview:

Untitled__1_page_

iPad

This is all possible on the iPad, give or take a few frustrating finger taps and Googling!

The user manual is here.